WO2008041065A1 - Rotary sonotrode for ultrasonic welding - Google Patents

Rotary sonotrode for ultrasonic welding Download PDF

Info

Publication number
WO2008041065A1
WO2008041065A1 PCT/IB2007/000026 IB2007000026W WO2008041065A1 WO 2008041065 A1 WO2008041065 A1 WO 2008041065A1 IB 2007000026 W IB2007000026 W IB 2007000026W WO 2008041065 A1 WO2008041065 A1 WO 2008041065A1
Authority
WO
WIPO (PCT)
Prior art keywords
sonotrode
sonotrode according
pins
groove
welding surface
Prior art date
Application number
PCT/IB2007/000026
Other languages
French (fr)
Inventor
Massimiliano Monti
Walter Sala
Original Assignee
Startec S.R.L.
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 Startec S.R.L. filed Critical Startec S.R.L.
Priority to EP07700452A priority Critical patent/EP2089214A1/en
Publication of WO2008041065A1 publication Critical patent/WO2008041065A1/en

Links

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
    • B29C66/83—General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools
    • B29C66/834—General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools moving with the parts to be joined
    • B29C66/8341—Roller, cylinder or drum types; Band or belt types; Ball types
    • B29C66/83411—Roller, cylinder or drum types
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B26—HAND CUTTING TOOLS; CUTTING; SEVERING
    • B26D—CUTTING; DETAILS COMMON TO MACHINES FOR PERFORATING, PUNCHING, CUTTING-OUT, STAMPING-OUT OR SEVERING
    • B26D7/00—Details of apparatus for cutting, cutting-out, stamping-out, punching, perforating, or severing by means other than cutting
    • B26D7/08—Means for treating work or cutting member to facilitate cutting
    • B26D7/086—Means for treating work or cutting member to facilitate cutting by vibrating, e.g. ultrasonically
    • 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
    • B29C65/083—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using ultrasonic vibrations using a rotary sonotrode or a rotary anvil
    • B29C65/085—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using ultrasonic vibrations using a rotary sonotrode or a rotary anvil using a rotary sonotrode
    • 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
    • B29C65/74—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area
    • B29C65/743—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area using the same tool for both joining and severing, said tool being monobloc or formed by several parts mounted together and forming a monobloc
    • B29C65/7443—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area using the same tool for both joining and severing, said tool being monobloc or formed by several parts mounted together and forming a monobloc by means of 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
    • B29C66/01—General aspects dealing with the joint area or with the area to be joined
    • B29C66/05—Particular design of joint configurations
    • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/114—Single butt joints
    • B29C66/1142—Single butt to butt joints
    • 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
    • B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
    • B29C66/41—Joining substantially flat articles ; Making flat seams in tubular or hollow articles
    • B29C66/43—Joining a relatively small portion of the surface of said articles
    • 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
    • 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
    • B29C66/81411—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 characterised by its cross-section, e.g. transversal or longitudinal, being non-flat
    • B29C66/81415—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 characterised by its cross-section, e.g. transversal or longitudinal, being non-flat being bevelled
    • B29C66/81417—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 characterised by its cross-section, e.g. transversal or longitudinal, being non-flat being bevelled being V-shaped
    • 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
    • B29C66/70—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
    • B29C66/71—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 composition of the plastics material of the parts to be joined
    • 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
    • B29C66/81—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
    • B29C66/812—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 composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B29C66/8122—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 composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps characterised by the composition of the material constituting the pressing elements, e.g. constituting 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
    • B29C66/9513—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 characterised by specific vibration frequency values or ranges
    • 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
    • B29K2905/00—Use of metals, their alloys or their compounds, as mould material
    • B29K2905/02—Aluminium
    • 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
    • B29K2905/00—Use of metals, their alloys or their compounds, as mould material
    • B29K2905/08—Transition metals
    • B29K2905/12—Iron

Definitions

  • the present invention relates to a sonotrode for ultrasonic welding according to the preamble of claim 1.
  • the invention particularly applies to the field of machines for the ultrasonic welding of plastic.
  • These machines comprise a generator of an electric signal having a frequency within the ultrasonic range, a converter which turns said electric signal into ultrasonic mechanic vibrations (e.g. through a piezoelectric device), and a sonotrode which, by vibrating on two adjacent portions of plastic, welds them together.
  • the sonotrode may be of stationary type (as described in patent EP0468125) or of rotary type (as described in patent EP0457187) .
  • the present invention relates to rotary sonotrodes, i.e. devices comprising a substantially discoidal rotary body which is rotated on two portions of plastic to be welded. The rotation has the effect of dragging the plastic, which otherwise should be pushed mechanically under the sonotrode (at the risk of wrinkles appearing on plastic films) .
  • One of the main problems suffered by known rotary sonotrodes lies in the fact that it is difficult to manufacture devices capable of vibrating at the desired frequency in order to obtain an effective transmission of the excitation energy to the plastic to be welded.
  • the sonotrode vibration amplitude may be drastically lowered by milling just a few tenths of a millimeter from the faces of the rotary body.
  • the main object of the present invention is to solve this drawback of the prior art, i.e. the problem of the difficulty in machining the sonotrode .
  • the invention is based on the general idea of providing a smooth groove around a pin being present on both opposite faces of the discoidal rotary body.
  • the pin comprises a fastening element, e.g. a bead or a threaded sleeve, adapted to connect the sonotrode to an arm subjected to rotary motion and to ultrasonic vibration.
  • a fastening element e.g. a bead or a threaded sleeve
  • the rotary sonotrode has a welding surface adapted to cut and weld plastic simultaneously.
  • Fig.l shows a detail of an ultrasonic welding machine according to the prior art
  • - Fig.2 shows a rotary sonotrode according to an embodiment of the present invention
  • Fig.3 shows the body of the sonotrode of Fig. 2 as viewed from the axis of rotation thereof;
  • - Fig.4 shows the body of a rotary sonotrode according to a second embodiment of the present invention
  • FIG. 5 shows the body of a rotary sonotrode according to a third embodiment of the present invention.
  • identical or equivalent items will be designated by the same reference number.
  • Fig. 1 shows a welding machine according to the prior art.
  • ' machine comprises a converter 1 adapted to generate ultrasonic vibrations and to rotate a shaft 2 (i.e. a driving member) coupled to a first arm 4 of sonotrode 5 through suitable bearings 3.
  • a converter 1 adapted to generate ultrasonic vibrations and to rotate a shaft 2 (i.e. a driving member) coupled to a first arm 4 of sonotrode 5 through suitable bearings 3.
  • body 50 of sonotrode 5 has a second arm 4 ' connected in a known manner to a suitable counterweight 6, which acts as a balancing member necessary for obtaining a substantially constant vibration amplitude on the whole surface of the rotary body coming in contact with materials 7 to be welded.
  • Fig.2 shows a first embodiment of a sonotrode according to the present invention.
  • the sonotrode is modular (i.e. made up of several interchangeable elements) and comprises a discoidal body 50 rotating about an axis of symmetry z indicated by a dashed line .
  • the term "discoidal” refers to any shapes of bodies having a disk-like shape, with substantially flat, concave or convex faces.
  • Body 50 is provided with removable fastening means 51 adapted to fasten it to arms 42.
  • fastening means 51 are beads which are screwed in corresponding threaded sleeves provided on arms 42, whereto shaft 2 and counterweight 6 are then constrained in a known manner.
  • arm 42 has been screwed on bead 51, the radial surfaces of arm 42 and of pin 54 are fastened together, thus forming a continuous cylindrical body similar to arm 4 of Fig.l.
  • Said continuous cylindrical body protrudes from the surface of face 53 by a length being equal to a multiple of half the wavelength corresponding to the preset work frequency.
  • Discoidal body 50 comprises a welding surface 52 adapted to be brought in contact with materials to be welded.
  • Reference number 53 designates a pair of opposite circular faces which, in the example of Fig.2, substantially extend in a plane being orthogonal to the axis of rotation.
  • Faces 53 have a peripheral portion joining welding surface 52 and an inner portion joining a pin 54.
  • the latter is surrounded by a suitably sized smooth annular groove 55.
  • Fig .3 shows the rotary body of the sonotrode of Fig .2 , as viewed by an observer standing on the axis of rotation. This drawing very shows clearly the position of groove 55, indicated by a broken line, around pin 54. As shown, the groove is external to pin 54, so that the groove remains open and visible even after body 50 has been coupled to arms 42.
  • groove 55 essentially is that element which allows to tune up the frequency of the rotary sonotrode, i.e. to obtain an effective operation thereof at the vibration frequency of the converter (e.g. 35kHz) .
  • Experimental tests have shown that the response of the sonotrode to machining is much less sensible when the removal of material is concentrated in an annular area adjacent to pin
  • the width of the welding surface in any case comprised between 0.1mm and
  • the groove consists of a ring being 27mm wide (ring having an inside diameter of 23mm and an outside diameter of 50mm) and
  • the sonotrode comprising such a discoidal body has a total vibration amplitude of 40 ⁇ m and allows to weld PVC at a constant speed of over 2 metres per minute.
  • the volume of material removed from the groove is approximately equal to 8% of the volume of a disc circumscribing discoidal body 50, i.e. a disc being as wide as the welding surface and with faces having the same diameter as faces 53 of body 50.
  • tests have been carried out by changing the diameter of faces 53, the width of welding surface 52 and the dimensions of the groove. These tests, carried out with 35kHz sonotrodes, have shown that a good vibration amplitude is obtained by keeping around 8%, in particular between 6% and 10%, the ratio between the volume of the groove and the volume of the cylinder circumscribing body 50, i.e. the cylinder having the same diameter as the body and having a height corresponding to the width of the welding surface .
  • the groove shall be: narrower and deeper, if the dimensions of the faces 53 are reduced, wider and less deep, if the dimensions of the faces 53 are increased.
  • the groove in order to tune up the sonotrode the groove must be modified as follows in comparison with the above-described example: the ring width must be reduced by about lmm (from 27mm to approx. 26mm) the depth must be increased by about 0.25mm (from 5mm to approx. 5.25mm)
  • Fig.4 shows a second embodiment example of a rotary sonotrode according to the present invention. Pins 54 do not protrude from faces 53, and are surrounded by the smooth groove 55.
  • Fig .5 shows a further example of embodiment of a sonotrode according to the present invention. The example of Fig.5 differs from the example of Figs .2 to 4 for two main elements. Firstly, fastening elements 51 are threaded sleeves adapted to receive beads being present on arms 42. Secondly, welding surface 52' is sharp. This shape of the welding surface allows to cut and weld plastic simultaneously.
  • fastening elements 51 are threaded sleeves adapted to receive beads being present on arms 42.
  • welding surface 52' is sharp. This shape of the welding surface allows to cut and weld plastic simultaneously.
  • Welding surface 52' comprises a pair of inclined surfaces 522 converging in a cutting surface 521.
  • cutting surface 521 of the rotary sonotrode cuts the plastic by dividing it into two parts, the edges of which are welded through the effect of inclined surfaces 522.
  • This embodiment is particularly advantageous for cutting sun curtains, e.g. made of a thermoplastic material, resined or smeared.
  • a sonotrode using the body 50 of Fig.3 in fact, allows to cut the curtain and to weld its edges, thus preventing them from fraying.
  • arms 42, pins 54 and discoidal body 50 may be one piece obtained by machining a single block of material.
  • shape of the sonotrode, and in particular its groove may be obtained either through a turning process, as described above, or else through a pressing process.
  • the groove lies as much as possible within the inner area of faces 53, but it is nonetheless possible to provide, between pins 54 and groove 55, a small flat transition area located substantially at the same level as faces 53.
  • faces 53 may have a concavity towards the inside of discoidal rotary body 50.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Forests & Forestry (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)

Abstract

A sonotrode for the ultrasonic welding of materials is described, wherein a discoidal body (50) rotating about an axis of symmetry (Z) comprises a peripheral welding surface (52) adapted to be brought in contact with materials to be welded, a pair of pins (51) for connecting said body (50) to driving or balancing members, and a pair of opposite faces (53) each having a peripheral portion joining said welding surface and an inner portion joining one of said pins. The pins are surrounded by a substantially smooth annular groove (55).

Description

ROTARY SONOTRODE FOR ULTRASONIC WELDING
DESCRIPTION
The present invention relates to a sonotrode for ultrasonic welding according to the preamble of claim 1.
The invention particularly applies to the field of machines for the ultrasonic welding of plastic. These machines comprise a generator of an electric signal having a frequency within the ultrasonic range, a converter which turns said electric signal into ultrasonic mechanic vibrations (e.g. through a piezoelectric device), and a sonotrode which, by vibrating on two adjacent portions of plastic, welds them together.
As known, the sonotrode may be of stationary type (as described in patent EP0468125) or of rotary type (as described in patent EP0457187) . The present invention relates to rotary sonotrodes, i.e. devices comprising a substantially discoidal rotary body which is rotated on two portions of plastic to be welded. The rotation has the effect of dragging the plastic, which otherwise should be pushed mechanically under the sonotrode (at the risk of wrinkles appearing on plastic films) . One of the main problems suffered by known rotary sonotrodes lies in the fact that it is difficult to manufacture devices capable of vibrating at the desired frequency in order to obtain an effective transmission of the excitation energy to the plastic to be welded. Once the material of the sonotrode has been established, its resonance frequency, i.e. the frequency at which the vibration amplitude is highest, largely depends on the machining of the two opposite faces of the discoidal body. Compared to an ideal embodiment, the sonotrode vibration amplitude may be drastically lowered by milling just a few tenths of a millimeter from the faces of the rotary body.
The main object of the present invention is to solve this drawback of the prior art, i.e. the problem of the difficulty in machining the sonotrode .
This object is achieved through a rotary sonotrode incorporating the features set out in the appended claims, which are intended as an integral part of the present description.
The invention is based on the general idea of providing a smooth groove around a pin being present on both opposite faces of the discoidal rotary body.
Advantageously, the pin comprises a fastening element, e.g. a bead or a threaded sleeve, adapted to connect the sonotrode to an arm subjected to rotary motion and to ultrasonic vibration.
In an advantageous embodiment, the rotary sonotrode has a welding surface adapted to cut and weld plastic simultaneously.
These and further objects of the present invention will become apparent from the following description and from the annexed drawings, which are supplied by way of non-limiting example, wherein:
Fig.l shows a detail of an ultrasonic welding machine according to the prior art; - Fig.2 shows a rotary sonotrode according to an embodiment of the present invention;
- Fig.3 shows the body of the sonotrode of Fig. 2 as viewed from the axis of rotation thereof;
- Fig.4 shows the body of a rotary sonotrode according to a second embodiment of the present invention;
- Fig.5 shows the body of a rotary sonotrode according to a third embodiment of the present invention; For clarity, in the present description identical or equivalent items will be designated by the same reference number.
Fig. 1 shows a welding machine according to the prior art. The
' machine comprises a converter 1 adapted to generate ultrasonic vibrations and to rotate a shaft 2 (i.e. a driving member) coupled to a first arm 4 of sonotrode 5 through suitable bearings 3.
On the opposite side to first arm 4, body 50 of sonotrode 5 has a second arm 4 ' connected in a known manner to a suitable counterweight 6, which acts as a balancing member necessary for obtaining a substantially constant vibration amplitude on the whole surface of the rotary body coming in contact with materials 7 to be welded.
The latter are placed under rotary body 5. For simplicity and clarity, no further details of the known machine of Fig.l will be specified herein, since the invention lies in the shape of sonotrode 5.
Fig.2 shows a first embodiment of a sonotrode according to the present invention. The sonotrode is modular (i.e. made up of several interchangeable elements) and comprises a discoidal body 50 rotating about an axis of symmetry z indicated by a dashed line .
In the present description, the term "discoidal" refers to any shapes of bodies having a disk-like shape, with substantially flat, concave or convex faces.
Body 50 is provided with removable fastening means 51 adapted to fasten it to arms 42.
In the example of Fig.2, fastening means 51 are beads which are screwed in corresponding threaded sleeves provided on arms 42, whereto shaft 2 and counterweight 6 are then constrained in a known manner. Once arm 42 has been screwed on bead 51, the radial surfaces of arm 42 and of pin 54 are fastened together, thus forming a continuous cylindrical body similar to arm 4 of Fig.l. Said continuous cylindrical body protrudes from the surface of face 53 by a length being equal to a multiple of half the wavelength corresponding to the preset work frequency. Discoidal body 50 comprises a welding surface 52 adapted to be brought in contact with materials to be welded. Reference number 53 designates a pair of opposite circular faces which, in the example of Fig.2, substantially extend in a plane being orthogonal to the axis of rotation.
Faces 53 have a peripheral portion joining welding surface 52 and an inner portion joining a pin 54. The latter is surrounded by a suitably sized smooth annular groove 55.
The term "smooth groove" refers to a groove having a smooth, or also corrugated, outer surface which in any case is not adapted to provide a stable connection, e.g. by means of a thread, to a latching element . Fig .3 shows the rotary body of the sonotrode of Fig .2 , as viewed by an observer standing on the axis of rotation. This drawing very shows clearly the position of groove 55, indicated by a broken line, around pin 54. As shown, the groove is external to pin 54, so that the groove remains open and visible even after body 50 has been coupled to arms 42.
Once the material (e.g. titanium, aluminium, steel, etc.) and the dimensions of the sonotrode (e.g. welding surface 52 of 30mm and diameter of faces 53 of 90mm) have been set, groove 55 essentially is that element which allows to tune up the frequency of the rotary sonotrode, i.e. to obtain an effective operation thereof at the vibration frequency of the converter (e.g. 35kHz) . Experimental tests have shown that the response of the sonotrode to machining is much less sensible when the removal of material is concentrated in an annular area adjacent to pin
54 than is obtained by machining other areas of faces 53. In other words, a sonotrode having an annular groove around the pin is simpler to manufacture, whatever the desired frequency
(in any case comprised between 10kHz and 10OkHz) and the width of the welding surface (in any case comprised between 0.1mm and
160mm) . Experimental tests have also shown that very good results are achieved when the material removed from the initially flat surfaces is concentrated to the extent of 80-100%, preferably of 90%, in the groove. Below is an example of a rotary sonotrode operating at 35kHz and having the following specifications :
- faces 53: diameter of 88.8mm
- pin 54 : diameter of 23mm
- welding surface: width of 30mm
- material: titanium The groove is obtained by removing material from face 53 through a turning operation.
The groove consists of a ring being 27mm wide (ring having an inside diameter of 23mm and an outside diameter of 50mm) and
5mm depth. The sonotrode comprising such a discoidal body has a total vibration amplitude of 40μm and allows to weld PVC at a constant speed of over 2 metres per minute.
In this example, the volume of material removed from the groove is approximately equal to 8% of the volume of a disc circumscribing discoidal body 50, i.e. a disc being as wide as the welding surface and with faces having the same diameter as faces 53 of body 50. Using the same material (although some variations are still possible among different batches) , tests have been carried out by changing the diameter of faces 53, the width of welding surface 52 and the dimensions of the groove. These tests, carried out with 35kHz sonotrodes, have shown that a good vibration amplitude is obtained by keeping around 8%, in particular between 6% and 10%, the ratio between the volume of the groove and the volume of the cylinder circumscribing body 50, i.e. the cylinder having the same diameter as the body and having a height corresponding to the width of the welding surface .
In practical terms, this translates into the fact that the diameter of faces 53 must be reduced as the width of the welding surfaces increases, while the volume of the groove is modified proportionally.
The tests have also shown that, once the volume of the groove has been set based on the volume of the disc circumscribing discoidal body 50, the groove shall be: narrower and deeper, if the dimensions of the faces 53 are reduced, wider and less deep, if the dimensions of the faces 53 are increased.
For example, if the diameter of faces 53 is 87.8mm (lmm less than in the example described above) , in order to tune up the sonotrode the groove must be modified as follows in comparison with the above-described example: the ring width must be reduced by about lmm (from 27mm to approx. 26mm) the depth must be increased by about 0.25mm (from 5mm to approx. 5.25mm)
Since the frequency response of the sonotrode depends also on the metallurgical characteristics of the materials used (e.g. titanium, aluminium or steel) , it can be assumed that the groove must have a volume in the range of 3% to 12% of the volume of the disc which is the central core of the discoidal body. Fig.4 shows a second embodiment example of a rotary sonotrode according to the present invention. Pins 54 do not protrude from faces 53, and are surrounded by the smooth groove 55. Fig .5 shows a further example of embodiment of a sonotrode according to the present invention. The example of Fig.5 differs from the example of Figs .2 to 4 for two main elements. Firstly, fastening elements 51 are threaded sleeves adapted to receive beads being present on arms 42. Secondly, welding surface 52' is sharp. This shape of the welding surface allows to cut and weld plastic simultaneously.
Welding surface 52' comprises a pair of inclined surfaces 522 converging in a cutting surface 521.
As it rotates, cutting surface 521 of the rotary sonotrode cuts the plastic by dividing it into two parts, the edges of which are welded through the effect of inclined surfaces 522.
This embodiment is particularly advantageous for cutting sun curtains, e.g. made of a thermoplastic material, resined or smeared. A sonotrode using the body 50 of Fig.3, in fact, allows to cut the curtain and to weld its edges, thus preventing them from fraying.
The advantages of the present invention are apparent from the above description.
It is also clear that many variations are possible without departing from the scope of the present invention as disclosed by the present description, the appended claims and the annexed drawings . For example, arms 42, pins 54 and discoidal body 50 may be one piece obtained by machining a single block of material. Additionally, the shape of the sonotrode, and in particular its groove, may be obtained either through a turning process, as described above, or else through a pressing process.
Also, it is important that the groove lies as much as possible within the inner area of faces 53, but it is nonetheless possible to provide, between pins 54 and groove 55, a small flat transition area located substantially at the same level as faces 53.
According to other variants, faces 53 may have a concavity towards the inside of discoidal rotary body 50.
* * * * * * *

Claims

1. Sonotrode for the ultrasonic welding of materials, wherein a discoidal body rotating about an axis of symmetry comprises : a peripheral welding surface adapted to be brought in contact with materials to be welded, a pair of pins for connecting said body to driving or balancing members , a pair of opposite faces each having a peripheral portion joining said welding surface and an inner portion joining one of said pins, characterized in that said pins are surrounded by a substantially smooth annular groove.
2. Sonotrode according to claim 1, characterized in that said faces are substantially circular and extend mostly in a plane being orthogonal to the axis of rotation.
3. Sonotrode according to claim 1, characterized in that said opposite faces (53) have a concavity toward the inside of said body.
4. Sonotrode according to any of the preceding claims, characterized by being modular.
5. Sonotrode according to claim 4, characterized in that said pins comprise removable fastening means (51) adapted to fasten said body to arms (42) of said sonotrode.
6. Sonotrode according to claim 5, characterized in that it is adapted to be excited at a preset work frequency, and that a pin and a respective arm form a body which protrudes from the surface of the face (53) by a length equal to a multiple of half the operating wavelength.
7. Sonotrode according to any of the preceding claims, characterized in that said groove has a volume comprised between 3% and 12% of the volume of a cylinder circumscribing said discoidal body (50) .
8. Sonotrode according to claim 7, characterized in that said groove has a volume equal to 8% of the volume of a cylinder circumscribing said discoidal body (50) .
9. Sonotrode according to any of claims 1 to 8, characterized by being made of titanium.
10. Sonotrode according to any of claims 1 to 8 , characterized by being made of steel .
11. Sonotrode according to any of claims 1 to 8, characterized by being made of aluminium.
12. Sonotrode according to any of the preceding claims, characterized in that said welding surface is adapted to cut plastic .
13. Sonotrode according to claim 12, characterized in that said welding surface comprises two inclined surfaces (522) converging in a cutting surface (521) .
* * * St *
PCT/IB2007/000026 2006-10-06 2007-01-08 Rotary sonotrode for ultrasonic welding WO2008041065A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP07700452A EP2089214A1 (en) 2006-10-06 2007-01-08 Rotary sonotrode for ultrasonic welding

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO2006A000718 2006-10-06
IT000718A ITTO20060718A1 (en) 2006-10-06 2006-10-06 ROTARY SONOTRODO FOR ULTRASOUND WELDING

Publications (1)

Publication Number Publication Date
WO2008041065A1 true WO2008041065A1 (en) 2008-04-10

Family

ID=38329305

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2007/000026 WO2008041065A1 (en) 2006-10-06 2007-01-08 Rotary sonotrode for ultrasonic welding

Country Status (3)

Country Link
EP (1) EP2089214A1 (en)
IT (1) ITTO20060718A1 (en)
WO (1) WO2008041065A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8601927B2 (en) 2009-11-30 2013-12-10 Geiss Ag Device for ultrasonic machining, machine tool and machine tool apparatus
CZ306798B6 (en) * 2016-03-30 2017-07-12 Mateiciuc A.S. A method of producing a building profile, a device for its implementation and the building profile

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0457187A2 (en) * 1990-05-18 1991-11-21 Kimberly-Clark Corporation Ultrasonic rotary horn and application of same
EP0894612A2 (en) * 1990-05-18 1999-02-03 Kimberly-Clark Worldwide, Inc. Ultrasonic rotary horn and application of same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0457187A2 (en) * 1990-05-18 1991-11-21 Kimberly-Clark Corporation Ultrasonic rotary horn and application of same
EP0894612A2 (en) * 1990-05-18 1999-02-03 Kimberly-Clark Worldwide, Inc. Ultrasonic rotary horn and application of same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8601927B2 (en) 2009-11-30 2013-12-10 Geiss Ag Device for ultrasonic machining, machine tool and machine tool apparatus
CZ306798B6 (en) * 2016-03-30 2017-07-12 Mateiciuc A.S. A method of producing a building profile, a device for its implementation and the building profile

Also Published As

Publication number Publication date
EP2089214A1 (en) 2009-08-19
ITTO20060718A1 (en) 2008-04-07

Similar Documents

Publication Publication Date Title
JP3796533B2 (en) Rotating acoustic horn
US5087320A (en) Ultrasonic rotary horn having improved end configuration
US3242029A (en) Ultrasonic sealer for sealing plastics
US3438824A (en) Method and apparatus for joining a closure to a container by high frequency radial vibrations
US7766067B2 (en) Rotary ultrasonic sealer
US8657182B2 (en) Torsion sonotrode, ultrasonic welding device and method for producing a welded connection by means of ultrasonic sound
KR100541197B1 (en) Rotary acoustic horn with sleeve
JP2000515060A (en) Stacked rotary acoustic horn
US6786384B1 (en) Ultrasonic horn mount
US7718022B2 (en) Resonant nodal mount for linear ultrasonic horns
US9469011B2 (en) Grinder and grinding machine
GB2282559A (en) Ultrasonic cutting device
WO2008041065A1 (en) Rotary sonotrode for ultrasonic welding
JP2016508884A (en) Ultrasonic collet horn for ultrasonic welding machine
US9908286B2 (en) Sonotrode with thickened portion
US5726519A (en) Traveling-wave piezoelectric motor
CH411416A (en) A method of applying static force and mechanical vibratory energy to a work area, in particular for performing vibration welding
US20050263520A1 (en) Sonotrode for carrying out cutting and welding operations on workpieces and method for the operation thereof
EP2227371B1 (en) Rotary horn for ultrasonic welding
KR101697198B1 (en) Ultrasonic welding apparatus
CN215847293U (en) Cutter and ultrasonic polishing equipment
US20210339336A1 (en) Ultrasonic Slotted Cylindrical Block Horn
WO2008087525A1 (en) Rotary sonotrode for ultrasonic cutting
JP2002035695A (en) Resonator for ultrasonic processing
WO2021111278A2 (en) Rotary acoustic horn

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 07700452

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2007700452

Country of ref document: EP