AU723618B2 - 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
AU723618B2
AU723618B2 AU56116/96A AU5611696A AU723618B2 AU 723618 B2 AU723618 B2 AU 723618B2 AU 56116/96 A AU56116/96 A AU 56116/96A AU 5611696 A AU5611696 A AU 5611696A AU 723618 B2 AU723618 B2 AU 723618B2
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AU
Australia
Prior art keywords
counterweight
arrangement
drive unit
groove
unit
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.)
Expired
Application number
AU56116/96A
Other versions
AU5611696A (en
Inventor
Magnus Rabe
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.)
Tetra Laval Holdings and Finance SA
Original Assignee
Tetra Laval Holdings and Finance SA
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 Tetra Laval Holdings and Finance SA filed Critical Tetra Laval Holdings and Finance SA
Priority to AU56116/96A priority Critical patent/AU723618B2/en
Publication of AU5611696A publication Critical patent/AU5611696A/en
Application granted granted Critical
Publication of AU723618B2 publication Critical patent/AU723618B2/en
Anticipated expiration legal-status Critical
Expired legal-status Critical Current

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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
    • 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
    • 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
    • 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
    • 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
    • B29C66/90—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
    • B29C66/9512—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 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
    • B29C66/84—Specific machine types or machines suitable for specific applications
    • B29C66/849—Packaging machines

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)

Description

I-'UU/U11 28/5/91 Regulation 3.2(2)
AUSTRALIA
Patents Act 1990
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT 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.
BACKGROUND ART A known ultrasound sealing unit consists of a converter, a booster and a horn. In the converter or transducer, which converts the electric oscillation into mechanical oscillation, some form of drive unit is included, this drive unit being coupled to an a.c. source. A known ultrasound sealing unit is described in Swedish Patent Application No. SE 9300918-1 (which is a compact sealing unit) which also possesses a drive unit. This sealing unit has a central nodal plane which constitutes the anchorage point of the unit, reaction bodies which surround the drive unit, and a horn with an elongate, narrow sealing surface.
Such a sealing unit has been particularly designed and produced for use in the limited space which is available in filling machines for filling liquid contents into packages of the single use disposable type.
A known drive unit for ultrasound sealing units consists of a number of piezoelectric ceramic plates which sandwich between them conductive metal S 20 sheets coupled to an a.c. source. The ceramic plates are secured to the sealing unit by means of a clamping screw which also clamps a counterweight S- in place.
Given that the clamping pressure which is normally applied to both counterweight and ceramic plates is relatively high, normally of the order of MPa or more, this results in even a relatively thick counterweight being deformed so much that the load distribution on the piezoelectric ceramic plates becomes distorted. The thickness of the counterweight is normally less than half of its diameter. Naturally, a thicker counterweight is subject to less deformation and would then give a more uniform load distribution on the ceramic plates. But it is a disadvantage to employ an excessively thick counterweight, since this in turn gives as a consequence that the ceramic plates must be fewer in number or thinner in dimensions. The uneven load Sdistribution gives rise to extreme, unfavourable loading on the ceramic plates.
The ceramic plates are brittle and highly sensitive to any form of tensile or flexural stress.
One method of obtaining a somewhat more uniform load distribution on the ceramic plates is to employ a horizontally divided counterweight.
However, the inherent disadvantage is that each part of the counterweight will be considerably thinner. This in turn leads to greater elasticity in each part and, as a result, totally uniform load distribution can never be achieved because of the inevitable deformation. In addition, a divided counterweight is more difficult and more expensive to manufacture. The greater degree of elasticity may also give rise to the generation of noise in the contact surfaces.
Furthermore, a quantifiably higher loss of energy has been demonstrated for divided counterweights.
OBJECTS OF THE INVENTION An object of the invention is to provide an improvement or alternative to the prior art.
A preferred object of the present invention is to realise a drive unit with a counterweight which distributes the loading when the sealing unit is in operation in as uniform a manner as possible, throughout the entire surface of the piezoelectric ceramic plates.
20 A further preferred object of the present invention is to be able to manufacture a counterweight for a drive unit which does not suffer from the drawbacks inherent in a divided counterweight.
SUMMARY OF INVENTION According to the present invention, there is provided an arrangement in 25 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 with an outer and inner periphery, and clamping means wherein a groove is provided in the inner periphery of the counterweight for the purpose of levelling out the clamping load.
The groove may be centrally placed in the inner periphery of the counterweight.
3 The groove may be V-shaped.
The groove in its major extent may constitute between 20 and percent of the thickness of the counterweight.
The groove may constitute between 15 and 40 percent of the material thickness of the counterweight.
The clamping means may be a screw.
The clamping load may be provided by the counterweight and the clamping means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS In order that the present invention might be more fully understood, an embodiment of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of an ultrasound sealing unit, Fig. 2 shows the load distribution of a known drive unit; Fig. 3 shows the load distribution of a drive unit according to an embodiment of the present invention; and .*Fig. 4 shows an embodiment of a drive unit according to the present invention.
l DESCRIPTION OF EMBODIMENT S 20 Every type of ultrasound sealing unit 1 must have a drive unit 2, like, for g example, the sealing unit 1 illustrated in Fig. 1. The sealing unit 1 in Fig. 1 has been specifically produced to be housed in the limited space available in those filling machines which pack liquid foods into packages of the single use disposable type, and the total length of the sealing unit 1 consists of but one 25 half of a wave length. In addition to the drive unit 2, the sealing unit 1 has reaction bodies 3 which surround the drive unit 2, a centrally placed nodal plane 4 in which the sealing unit may be fixed, and a horn 5 with an elongate, narrow sealing surface 6. The arrangement according to the present embodiment may be employed for drive units 2 for ultrasound sealing units 1 of the type which consists of a converter, a booster and a horn.
The drive unit 2 of the sealing unit 1 which is connected to an a.c.
source (not shown) converts the electric potential into mechanical displacement which gives rise to the oscillation which constitutes the sealing work of the unit 1. The drive unit 2 consists of a number of piezoelectric ceramic plates 7 with an outer and an inner periphery. Between the piezoelectric ceramic plates 7 there are provided conductive metal sheets 8, preferably manufactured from nickel or beryllium bronze. The metal sheets 8 are connected to an a.c. source (not shown) so that the piezoelectric ceramic plates 7 are electrically connected in parallel.
The piezoelectric ceramic plates 7 withstand extreme compression stresses, but they are brittle and sensitive to tensile and flexural stresses.
Consequently, while the ultrasound sealing unit 1 is in operation, the piezoelectric ceramic plates 7 must be under pressure loading, which is realised by a clamping force which is higher than the highest amplitude generated by the drive unit 2. This clamping force or load is achieved by a counterweight 9 and a clamping means in the form of clamping screw The counterweight 9 which consists of a metal plate with an outer and inner periphery is manufactured from a material which should be as rigid as possible, for example steel. The counterweight 9 is employed partly to distribute the clamping force over the piezoelectric ceramic plates 7 and partly as a reaction mass to obtain the specific resonance frequency which it is 20 intended that the drive unit 2 is to excite. The clamping screw 10 holds together the counterweight 9, the ceramic plates 7 and the metal sheets 8 to a unit under a certain clamping force, and also secures the drive unit 2 in the ooo -sealing unit 1.
It is desirable that the clamping force or load which is applied on the 25 ceramic plates 7 be as uniformly distributed as possible, given that the ceramic plates 7 are sensitive to uneven loading. However, measurements have shown that a known counterweight, as in Fig. 2, is deformed by the high clamping pressure, normally of the order of magnitude of 25 MPa or more, so that a higher compression loading is obtained at the inner periphery of the counterweight 9 than at its outer periphery. It is particularly unfortunate to have the maximum loading at the edge of the ceramic plates 7, since the ceramics are extremely brittle. This problem has been solved to some degree by employing a divided counterweight 9 which gives a slightly more uniform load distribution. However, as a result of a divided counterweight, the counterweight itself 9 will be thinner and thereby more elastic. As a result, wholly uniform load distribution cannot be achieved because of the inevitable deformation of the parts of the counterweight. Because of the increased elasticity, noise may moreover be generated in the contact surfaces of the thin parts of the divided counterweight 9. In addition, a divided counterweight 9 gives quantifiable energy losses.
The intention is to achieve a distribution of the clamping load as shown in Fig. 3. This is achieved according to the present embodiment by, as shown in Figs. 3 and 4, providing grooves 12 in the inner periphery of the counterweight 9. By providing grooves 12 in the inner periphery of the counterweight 9, the force lines which follow the material in the counterweight 9 are urged out towards the outer periphery and a clamping load which is distributed uniformly over the entire surface of the ceramic plates 7 will thus be obtained even when the thickness of the counterweight is less than half of its diameter.
The groove 12 runs around the entire inner periphery of the counterweight 9 and should be centrally placed in the counterweight 9. The 20 groove 12 may be straight, U-or V-shaped. The groove 12 should further have a gentle radius 13, i.e. as large a radius 13 as possible. In the preferred embodiment, the groove 12 is V-shaped. Smaller radii 13 or straight corners may give rise to fatigue cracks in the material of the counterweight 9. The groove 12 should, in its major extent, constitute 20-80 percent of the thickness 25 A of the counterweight 9. In the preferred embodiment, the groove 12 constitutes 40-50 percent of the thickness A of the counterweight 9. The depth of the groove 12 is between 15 and 40 percent of the material thickness S B of the counterweight 9 between the inner and outer peripheries; in the preferred embodiment the depth of the groove 12 is between 20 and percent of the material thickness B of the counterweight 9. As shown in Figs.
3 and 4, the counterweight 9 may have different diameters. In the upper portion of the counterweight 9, the inner diameter D1 is determined by the 6 diameter of the clamping screw 10 and, in the lower portion of the counterweight 9, the inner diameter D2 is determined by the inner diameter of the ceramic plates 7. Diameter D2 should be the same as the inner diameter of the ceramic plates 7.
As will have been apparent from the foregoing description, embodiments of the present invention realise an arrangement in a drive unit 2 for an ultrasound sealing unit 1 which affords a more uniform load distribution of the clamping load on the ceramic plates 7. This arrangement results in a drive unit 2 which is more efficient than known drive units 2 and the arrangement also gives the drive unit 2 longer service life.
The present invention should not be considered as restricted to the exemplary embodiment described above and shown with reference to the drawings, many modifications being conceivable without departing from the spirit and scope of the invention as defined by the appended claims.
09 0 0@*o00 0e 0 0000U 0•O @000

Claims (8)

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 with an outer and inner periphery, and clamping means wherein a groove is provided in the inner periphery of the counterweight for the purpose of levelling out the clamping load.
2. The arrangement as claimed in Claim 1, wherein the groove is centrally placed in the inner periphery of the counterweight.
3. The arrangement as claimed in claim 1 or 2, wherein the groove is V- shaped.
4. The arrangement as claimed in Claim 1, characterized in that the groove in its major extent constitutes between 20 and 80 percent of the Sthickness of the counterweight.
5. The arrangement as claimed in Claim 1, characterized in that the groove constitutes between 15 and 40 percent of the material thickness of the counterweight. one
6. The arrangement as claimed in any one of claims 1 to 5 wherein the clamping means is a screw. 0
7. An arrangement as claimed in any one of the preceding claims wherein the clamping load is provided by the counterweight and the clamping means. 8
8. An arrangement in a drive unit for an ultrasound sealing unit substantially as hereinbefore described and illustrated with reference to Figures 3 and 4 of the accompanying drawings. DATED this 2nd day of June, 2000 TETRA LAVAL HOLDINGS FINANCE SA WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP/RJS/MEH P10048AU00.DOC e o *o g o• *g ••go go *ooo
AU56116/96A 1996-06-21 1996-06-21 An arrangement in a drive unit for an ultrasound sealing unit Expired AU723618B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU56116/96A AU723618B2 (en) 1996-06-21 1996-06-21 An arrangement in a drive unit for an ultrasound sealing unit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AU56116/96A AU723618B2 (en) 1996-06-21 1996-06-21 An arrangement in a drive unit for an ultrasound sealing unit

Publications (2)

Publication Number Publication Date
AU5611696A AU5611696A (en) 1998-01-08
AU723618B2 true AU723618B2 (en) 2000-08-31

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5508580A (en) * 1990-05-24 1996-04-16 Canon Kabushiki Kaisha Vibration wave driven motor
EP0615907B1 (en) * 1993-03-19 1997-10-15 Tetra Laval Holdings & Finance SA A device for ultrasonic sealing

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5508580A (en) * 1990-05-24 1996-04-16 Canon Kabushiki Kaisha Vibration wave driven motor
EP0615907B1 (en) * 1993-03-19 1997-10-15 Tetra Laval Holdings & Finance SA A device for ultrasonic sealing

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Publication number Publication date
AU5611696A (en) 1998-01-08

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