AU723621B2 - An arrangement in a drive unit for an ultrasound sealing unit - Google Patents

An arrangement in a drive unit for an ultrasound sealing unit Download PDF

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Publication number
AU723621B2
AU723621B2 AU56117/96A AU5611796A AU723621B2 AU 723621 B2 AU723621 B2 AU 723621B2 AU 56117/96 A AU56117/96 A AU 56117/96A AU 5611796 A AU5611796 A AU 5611796A AU 723621 B2 AU723621 B2 AU 723621B2
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Australia
Prior art keywords
gasket
arrangement
sealing unit
ceramic plates
unit
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AU56117/96A
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AU5611796A (en
Inventor
Magnus Rabe
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Tetra Laval Holdings and Finance SA
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Tetra Laval Holdings and Finance SA
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Priority to AU56117/96A priority Critical patent/AU723621B2/en
Publication of AU5611796A publication Critical patent/AU5611796A/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/08—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using ultrasonic vibrations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B3/00—Methods or apparatus specially adapted for transmitting mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/814—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps
    • B29C66/8141—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined
    • B29C66/81427—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined comprising a single ridge, e.g. for making a weakening line; comprising a single tooth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/814—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps
    • B29C66/8145—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the constructional aspects of the pressing elements, e.g. of the welding jaws or clamps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/816—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the mounting of the pressing elements, e.g. of the welding jaws or clamps
    • B29C66/8167—Quick change joining tools or surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/95—Measuring or controlling the joining process by measuring or controlling specific variables not covered by groups B29C66/91 - B29C66/94
    • B29C66/951—Measuring or controlling the joining process by measuring or controlling specific variables not covered by groups B29C66/91 - B29C66/94 by measuring or controlling the vibration frequency and/or the vibration amplitude of vibrating joining tools, e.g. of ultrasonic welding tools
    • B29C66/9516—Measuring or controlling the joining process by measuring or controlling specific variables not covered by groups B29C66/91 - B29C66/94 by measuring or controlling the vibration frequency and/or the vibration amplitude of vibrating joining tools, e.g. of ultrasonic welding tools by controlling their vibration amplitude
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
    • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
    • B29C66/7232—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer
    • B29C66/72321—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer consisting of metals or their alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
    • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
    • B29C66/7232—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer
    • B29C66/72327—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer consisting of natural products or their composites, not provided for in B29C66/72321 - B29C66/72324
    • B29C66/72328—Paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/739—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/7392—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic
    • B29C66/73921—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic characterised by the materials of both parts being thermoplastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/84—Specific machine types or machines suitable for specific applications
    • B29C66/849—Packaging machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2705/00—Use of metals, their alloys or their compounds, for preformed parts, e.g. for inserts
    • B29K2705/02—Aluminium

Description

1 i R /UU/U11 28/5/91 Regulation 3.2(2)
AUSTRALIA
Patents Act 1990
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT e r Application Number: Lodged: Invention Title: AN ARRANGEMENT IN A DRIVE UNIT FOR AN ULTRASOUND SEALING
UNIT
The following statement is a full description of this invention, including the best method of performing it known to us AN ARRANGEMENT IN A DRIVE UNIT FOR AN ULTRASOUND SEALING UNIT TECHNICAL FIELD The present invention relates to an arrangement in a drive unit for an ultrasound sealing unit, and relates particularly to a drive unit which includes a number of piezoelectric ceramic plates which are disposed with interjacent, conductive metal sheets, electrically coupled to an a.c. source, a counterweight and clamping means, the ultrasound sealing unit comprising a homogenous body on which the drive unit is fixedly mounted.
BACKGROUND ART Different types of units for sealing by ultrasound are in industrial use today. Swedish Patent Application No. SE 9300918-1 discloses an ultrasound sealing unit which has been particularly developed for use in filling machines of the type which fills liquid foods into packages of the single use disposable type. There is but limited space available in these filling machines for an ultrasound sealing unit, and so the described unit is of a type which has a total length of one half of a wave length. In the filling machine, a material web of a laminate packaging material is formed into a tube which is sealed by a longitudinal joint or seam seal and is filled with the intended contents. The filled material tube is transversely sealed and, in these transverse seals, the material tube is severed to form individual packaging containers. The described sealing unit is intended for the transverse joint seals, for which reason the sealing unit displays an elongate, narrow sealing surface whose width corresponds to the width of the transverse joint seal. In order to achieve the requisite length of the transverse seal, a number of the above described sealing units must be built together to form a composite ultrasound sealing equipment unit. The sealing unit displays reaction bodies 30 surrounding the drive unit, a horn which carries the elongate, narrow Sesealing surface, and a centrally located nodal plane where the amplitude of the unit is zero and where the unit may be secured in the filling machine.
A sealing unit of the above-outlined type will have an extremely complex geometry. Although, in the centrally located nodal plane, there is an amplitude which is zero, and although this nodal plane is employed for securing the unit, there is a slight residual motion in this plane because of the oscillation of the unit. This motion may be described as an undulation in one plane. The ceramic plates in the drive unit withstand considerable compression loading, but are brittle and highly sensitive to any type of flexural and tensile loading, for which reason the residual motion in the nodal plane may cause the ceramic plates to crack.
When a number of the above-described units are combined together to form an ultrasound sealing equipment unit in a filling machine, and when several filling machines may be employed in the same premises, it is vitally important that the different sealing units operate at the same amplitude in order to ensure complete exchangeability of parts. The piezoelectric ceramic plates are difficult to obtain with uniform characteristics, for which reason different drive units may have minor variations in the amplitude generated.
OBJECTS OF THE INVENTION An object of the present invention is to be able to manufacture a drive unit in which the minor residual flexural stresses in the nodal plane are reduced to such a low level that they do not constitute a harmful movement for the sensitive ceramic plates.
A preferred object of the present invention is to be able to manufacture drive units which can operate at a predetermined and preselected amplitude 20 without the quality of the piezoelectric ceramic plates governing the amplitude.
SUMMARY OF INVENTION According to the present invention there is provided an arrangement in S.a drive unit for an ultrasound sealing unit, the drive unit having a number of piezoelectric ceramic plates which are disposed with interjacent, conductive metal sheets that are electrically coupled to an a.c. source, a counterweight and clamping means for mounting the drive unit, the ultrasound sealing unit including a homogenous body on which the drive unit is fixedly mounted, wherein, between the ceramic plates and the homogenous body, there is provided a gasket which constitutes a spacer between the homogenous body and the ceramic plates, said gasket being adapted to permit the oscillation of 2a the ultrasound sealing unit, but being adapted to prevent residual flexural stresses from reaching the drive unit.
Preferably, the gasket is manufactured from a material having a modulus of elasticity that is lower than the material from which the homogenous body of the ultrasound sealing unit is manufactured, and that is lower than the modulus of elasticity of the ceramic plates.
Preferably, the contact surface of the gasket against the ceramic plates is identical to the contact surface of the ceramic plates against the gasket.
Preferably, the homogenous body of the ultrasound sealing unit is manufactured from titanium; and that the gasket is manufactured from aluminium.
Alternatively, the homogenous body of the ultrasound sealing unit is manufactured from aluminium; and that the gasket is manufactured from chromium.
Preferably, the gasket has a height such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
Preferably, the gasket is selected from a material of a predetermined modulus of elasticity, such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
20 The size of the contact surface of the gasket against the body of the ultrasound sealing unit may be selected such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
The clamping means may be a screw.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS One preferred embodiment of the present invention will now be described in greater detail hereinbelow, by way of example only, with particular reference to the accompanying Drawings, in which: Fig. 1 is a schematic diagram of an ultrasound sealing unit; Fig. 2 is a schematic diagram of the distribution of the tension around the nodal plane of the sealing unit; and Fig. 3 shows a drive unit according to the present embodiment.
DESCRIPTION OF PREFERRED EMBODIMENT The arrangement according to the present embodiment has been specifically developed and produced for an ultrasound sealing unit 1 of the type which is shown in Fig. 1, or similar sealing units 1. The sealing unit 1 substantially consists of a drive unit 2 and a homogeneous body 13.
The drive unit 2 of the sealing unit 1 consists of a number of piezoelectric ceramic plates 3 with interjacent, conductive metal sheets 4. The metal sheets 4 are coupled to an a.c. source (not shown), so that the piezoelectric ceramic plates 3 are electrically connected in parallel. The ceramic plates 3 and metal sheets 4, together with a counterweight 5, are 10 held together under pretensioning by a clamping screw 6. The clamping screw 6 is also employed to secure the drive unit 2 in the body 13 of the sealing unit 1. The drive unit 2 converts the electric potential into a mechanical displacement which gives rise to the oscillation that constitutes the sealing work of the unit 1.
The body 13 of the sealing unit 1 consists of reaction bodies 7 which surround the drive unit 2, and a horn 8 with an elongate, narrow sealing surface 9. The purpose of the reaction bodies 7 is to absorb the oscillations that occur on oscillation of the horn 8. Between the horn 8 and the reaction bodies 7, there is formed a nodal plane 10 where the amplitude of the unit 1 •20 is zero. The nodal plane 10 is provided with an anchorage edge 11 in which the sealing unit may be fixed. The reaction bodies 7 of the sealing unit 1, the Sonodal plane 10 with its anchorage edge 11, and the horn 8 are preferably manufactured from titanium, but may also be manufactured from aluminium. The body 13 of the sealing unit 1 is in the preferred embodiment of one piece manufacture as a homogeneous body, but the parts may of course be manufactured separately and subsequently assembled to form a body 13.
The above described sealing unit 1 has been particularly designed and produced for use in filling machines of the type which fills liquid foods into packaging containers of the single use disposable type. In these filling machines, there is but limited space available for an ultrasound sealing unit, in particular when the intention is to employ such equipment as a retrofit in already existing machines without these needing to be reconstructed or redesigned to any appreciable degree. The sealing unit, according to Fig. 1, therefore has a total length of one half of a wavelength. In the filling machine which operates with a continuous material web of a laminate with paper or paperboard and thermoplastic, as well as possibly aluminium, this material web is formed into a tube with a longitudinal joint or seam seal. The tube is filled with the intended contentents and individual packaging containers are produced by means of transverse joint seals in which the material web is severed. The sealing unit I according to Fig. 1 is intended to be employed for transverse joint seals, for which reason the horn S of the unit 1 is terminated by an elongate, narrow sealing surface 9. The width of the sealing surface 9 corresponds to the width of the transverse joint seal. In order to achieve the 20 requisite length of the transverse joint seal, a number of sealing units 1 must be integrated together to form a complete unit of sealing equipment.
Given that an ultrasound sealing unit 1 of the above described type will have an extremely complicated geometry, there will be a minor residual motion in the nodal plane 10 even though the amplitude in the nodal plane 10 is zero. As shown in the lower part of Fig. 2, this motion consists of a combined longitudinal oscillation and a flexural oscillation. The motion may be described as an undulation movement in one plane. The intention is that only the longitudinal oscillation, the oscillation of the ultrasound sealing unit 1 which is required for the work of the unit 1, be propagated further to the 30 ceramic plates 3 in the drive unit 2. The piezoelectric ceramic plates 3 withstand considerable compression loading, but they are brittle and are extremely sensitive to tensile and flexural stresses. It is therefore desirable that only the longitudinal oscillations, as shown in the upper part of Fig. 2, be propagated to the ceramic plates 3 in the drive unit 2.
This problem is solved in that the arrangement according to the present embodiment consists of a gasket 12 of the same dimensions as the ceramic plates 3, the gasket being placed between the ceramic plates 3 and the nodal plane 10 of the sealing unit 1. The gasket is held in place by the clamping screw 6 which, at high pressure, holds together the ceramic plates 3, the metal sheets 4 and the counterweight 5. The gasket 12 will constitute a spacer H between the ceramic plates 3 and the body 13 of the sealing unit 1.
The gasket 12 should be manufactured from a material which does not damp the longitudinal oscillations that are fundamental to the sealing work of the sealing unit 1, i.e. the material must have a high Q value. On the other hand, the gasket 12 must weaken the harmful flexural oscillations so that they cannot destroy the fragile ceramic plates 3. The gasket is, therefore, manufactured from a material which has a lower modulus of elasticity than the materials that surround the gasket 12, i.e. the modulus of elasticity of the ceramics which lies at approximately 75-120 GPa and the modulus of elasticity of the material from which the body 13 of the sealing unit 1 is 15 manufactured. The nodal plane 10 with anchorage edge 11, reaction bodies 7 ~and horn 8 which together constitute a homogeneous body 13, are normally manufactured from titanium which has a modulus of elasticity of approximately 110 GPa. In the preferred embodiment, the gasket 12 is manufactured from aluminium which has a modulus of elasticity of 70 GPa.
In the case when the homogeneous body 13 in the unit 1 is manufactured from aluminium, the gasket 12 should be selected from a material possessing a lower modulus of elasticity than aluminium, such as, for example, chromium or bismuth. An alternative is to employ a gasket of the same or ~higher modulus of elasticity than any of the surrounding materials, i.e. the ceramics or the material of the body 13. However, experiments have shown that the results of the work of the sealing unit 1 will be improved when use is made of a material in the gasket 12 possessing a lower modulus of elasticity.
Since the surface of the nodal plane 10 in which the drive unit 2 is to be secured is difficult to manufacture in titanium so as to be completely smooth and even, the soft aluminium gasket 12 will even out any possible unevenness. The soft aluminium surface is moreover easy to form and shape so that the abutment of the gasket 12 against the ceramic plates 3 will be as flat as possible.
When a number (preferably three) of sealing units 1 are built together in a filling machine in order to achieve a sufficiently long transverse seal, there are extremely strict demands that the units must work at the same amplitude. Several filling machines may, in addition, be in operation in the same premises, for which reason exchangeability of the sealing units 1 must be total. The piezoelectric ceramic plates 3 are, however, difficult to manufacture with exactly the same characteristics in all respects, for which reason discrepancies may give rise to variations in the amplitude of the different units 1. By varying the thickness dimensions of the gasket 12 lying between the ceramic plates 3 and the nodal plane 10, it is possible to govern the amplitude of the drive unit 2 to a predetermined and preselected amplitude. The amplitude is modified such that a thinner gasket 12 gives a lower amplitude and a thicker gasket 12 gives a higher amplitude. The amplitude is modified because of the fact that the electro-mechanical coupling factor is changed.
One alternative to modifying the thickness of the gasket 12 is to change the material in the gasket 12 to a material with a different modulus of elasticity. A further alternative is to vary the size of the contact surface or interface between the gasket 12 and the body 13 on the sealing unit 1. The surface of the gasket 12 against the ceramic plates 3 should, however, be equal to the surface of the ceramic plates 3. The preferred alternative which 20 is most economical and most easily manufactured is, however, the firstmentioned in which the height H of the gasket 12 is varied so as to obtain the desired amplitude.
By calibrating the ceramic plates 3, it is possible to select a specific c: gasket 12 and thereby, already in the manufacturing stage of the ultrasound sealing unit 1, obtain units 1 which all operate at the same amplitude.
As will have been apparent from the foregoing description, the arrangement according to the present embodiment realises a drive unit 2 in which residual flexural oscillations in the nodal plane 10 of the unit 1 are not propagated to the sensitive ceramic plates 3 in the drive unit 2.
Employing the arrangement according to the present embodiment, it is moreover possible to realise a control of all manufactured sealing units so that they all operate at the same amplitude. This amplitude is otherwise governed by discrepancies in the characteristics of the ceramic plates 3, for which reason it is possible to reduce the standard requirements on the ceramic plates 3.
7 The present invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the spirit and scope of the appended Claims.
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Claims (12)

1. An arrangement in a drive unit for an ultrasound sealing unit, the drive unit having a number of piezoelectric ceramic plates which are disposed with interjacent, conductive metal sheets that are electrically coupled to an a.c. source, a counterweight and clamping means for mounting the drive unit, the ultrasound sealing unit including a homogenous body on which the drive unit is fixedly mounted, wherein, between the ceramic plates and the homogenous body, there is provided a gasket which constitutes a spacer between the homogenous body and the ceramic plates, said gasket being adapted to permit the oscillation of the ultrasound sealing unit, but being adapted to prevent residual flexural stresses from reaching the drive unit.
2. The arrangement as claimed in Claim 1, wherein the gasket is manufactured from a material having a modulus of elasticity that is lower than the material from which the homogenous body of the ultrasound sealing unit is manufactured, and that is lower than the modulus of elasticity of the ceramic plates.
3. The arrangement as claimed in Claim 1, wherein the contact surface of the gasket against the ceramic plates is identical to the contact surface of the ceramic plates against the gasket. S.
4. The arrangement as claimed in Claim 1, wherein the homogenous body of the ultrasound sealing unit is manufactured from titanium; and that the gasket is manufactured from aluminium.
The arrangement as claimed in Claim 1, wherein the homogenous body of the ultrasound sealing unit is manufactured from aluminium; and that the gasket is manufactured from chromium.
6. The arrangement as claimed in any one of the preceding Claims, wherein the gasket has a height such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
7. The arrangement as claimed in any one of Claims 1 to 5, wherein the gasket is selected from a material of a predetermined modulus of elasticity, such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
8. The arrangement as claimed in any one of Claims 1 to 5, wherein the size of the contact surface of the gasket against the body of the ultrasound sealing unit is selected such that the amplitude of the ultrasound sealing unit is governed to a predetermined, preselected amplitude.
9. The arrangement as claimed in any one of claims 1 to 8 wherein the clamping means is a screw. 9
10. The arrangement as claimed in any one of the claims 1 to 9 wherein the gasket is placed between the ceramic plates and the nodal plane of the sealing unit.
11. The arrangement as claimed in claim 1 wherein the gasket has the same or higher modulus of elasticity than the material of the ceramic plates and the homogenous body. goo* 0 0 9
12. An arrangement in a drive unit according to either claim 4 or substantially as hereinbefore described and illustrated with reference to the accompanying drawings. DATED this 17th day of March, 2000 TETRA LAVAL HOLDINGS FINANCE SA WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP/RJS/MEH P10049AU00.DOC f **S *o* 9e e*
AU56117/96A 1996-06-21 1996-06-21 An arrangement in a drive unit for an ultrasound sealing unit Expired AU723621B2 (en)

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Application Number Priority Date Filing Date Title
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AU723621B2 true AU723621B2 (en) 2000-08-31

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107116019A (en) * 2017-06-27 2017-09-01 哈尔滨工业大学深圳研究生院 Bifrequency ultrasonic vibrating machining transducer and its mode of operation

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4607185A (en) * 1985-02-01 1986-08-19 American Hospital Supply Corporation Ultrasonic horn assembly
DE4014846A1 (en) * 1990-05-09 1991-11-14 Schmidbauer Kg Elma Hans Ultrasonic oscillator for liquid bath cleaning applications - has one or more PXE rings in contact with electrode-insulator layer
EP0615907B1 (en) * 1993-03-19 1997-10-15 Tetra Laval Holdings & Finance SA A device for ultrasonic sealing

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4607185A (en) * 1985-02-01 1986-08-19 American Hospital Supply Corporation Ultrasonic horn assembly
DE4014846A1 (en) * 1990-05-09 1991-11-14 Schmidbauer Kg Elma Hans Ultrasonic oscillator for liquid bath cleaning applications - has one or more PXE rings in contact with electrode-insulator layer
EP0615907B1 (en) * 1993-03-19 1997-10-15 Tetra Laval Holdings & Finance SA A device for ultrasonic sealing

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