NL8301424A - DEVICE AND METHOD FOR OSCILLATLY JOINTING TWO OBJECTS FROM THERMOPLASTIC MATERIAL - Google Patents

Abstract

Methods and apparatus are disclosed for the bonding together of two similarly shaped articles of similar thermoplastic material utilizing oscillatory motion between the two articles to generate frictional heat therein sufficient to form an hermetic seal therebetween. <IMAGE>

Description

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Apparatus and method for oscillatingly connecting two objects of thermoplastic material.

The invention generally relates to joining two correspondingly shaped parts of thermoplastic articles together and more particularly to frictional welding of upper and lower container sections to obtain a single hermetically welded container.

Known is a method of welding container sections to obtain a single container, which method is directed to cylindrically shaped thermoplastic containers which are rotated together at high speeds to generate heat by friction to connecting the two sections.

This known method may be referred to as "spin welding" and is described, for example, in U.S. Patents 3,297,504 Re. 29,448 and 3,499,068.

Although this method offers advantages over methods such as chemical bonding, bonding and thermal bonding by means of a laser beam, electron beam, radio waves and electrical means, a drawback is that the method is limited to cylindrical joints. Obviously, two non-cylindrical container sections cannot be spun-welded together, as their surfaces would not be in continuous contact with each other during the relative twisting motion of the two parts.

The present invention now overcomes this drawback of spin welding by providing methods and devices for frictional welding of thermoplastic containers with non-cylindrical joining sections, while the method of the invention is also suitable for use in cylindrical sections.

The present invention uses oscillating movements, not rotary movements, between the two sections to be joined together to provide the friction for generating heat whereby the two sections can be joined together. nnen are connected.

The invention will now be explained in more detail with reference to illustrative embodiments, shown in the drawing, in which: Fig. 1-3 show cross sections over three different types of container connections, which can be effected using the present invention; Fig. 4 shows a partial side view of an oscillating welding device for low-frequency welding; Figure 5 shows a schematic view of a rotary air-oscillator connection for use with the device of Figure 4? Fig. 6 shows a partial view of an oscillating welding device for high-frequency welding? Figure 7 shows a schematic diagram of the rotary connection for supplying air and electrical power to the device of Figure 6; and Fig. 8 shows a schematic top view of the rotating feed and discharge system for the oscillating welding device.

The present invention is a modification and improvement of the device described in US Patents 3,499,068 and Re. 29,448. For the sake of clarity of description, the invention will be described only with reference to one station of a multi-station system, such as the multi-station systems described in the above-mentioned US patents. With the exception of the modifications described with respect to the single station shown, the remainder of the container forming system according to the invention corresponds to that of said patents.

Fig. 4 is a side view of the single station 10 of the interconnection system 11. This single station is an example of the other stations included in the multi-station rotary system. The station includes an upper bearing assembly 12 mounted on rollers and an upper curves track head 13. The 8301424 lower bearing assembly 14 is mounted in a lower curve web assembly 15 by roller tracking means. 16. The top assembly 12 is mounted in the curve track head 13 by means of the follower roller 17.

The top head 13 generally includes a generally circular vertical curve plate 18 in which a circumferential curve groove 19 is provided. The groove 19 extends around the head 13 and receives the follower roller 17 in such a way that it fits tightly therein. The groove 19 extends in the vertical direction as indicated by 20 to obtain a certain vertical displacement of the support assembly 12 when it is rotated about the head 13.

Likewise, the lower cam track assembly 15 includes a circumferential groove 21 extending around the entire head 15 and receiving a follower roller 16 rotatable therein. The groove 21 also extends vertically to provide vertical displacement of the lower assembly 14 relative to the upper assembly 12.

The lower assembly 14 generally includes a vertical shaft support 22, to which is attached a lower tool 23 for receiving and firmly clamping the lower part of the container to be connected. The tool 23 preferably has an upwardly directed internal cavity, the shape of which is similar to that of the bottom holder part to be connected to the top holder part. Furthermore, the tool 23 has known means such as a vacuum system for receiving the bottom holder part therein.

The upper carrier head '12 is connected by the shaft 24 to the follower roller 17. The roller 17 is rotatably mounted on the shaft 24. The carrier head 12 also contains an air oscillator 25, which acts via an pin connection 26 on an oscillating diaphragm 27, which in turn is fixedly connected to the carrying head 12. The oscillator 25 has a sliding shaft 28 which projects downwardly and to which is connected an upper tool shaft 29, which carries an upper tool 30. The tool shaft 29 passes through an air bearing 31 mounted in an bearing housing 40 32 which is fixedly connected to the carrying head 12. The air bearing 8301424 * ί> -4- 31 allows for vertical sliding movement between the spindle 29 and the bearing assembly 12. The upper tool 30 has known means such as vacuum means for gripping the top part of the holder 5 to be connected to the bottom part received in the tool 23. An air supply source 33 supplies air to the bearing 31, a second air supply source 34 supplies air to the oscillator 25, and a third air supply source 35 supplies air to the diaphragm 27. The oscillation diaphragm 27 is connected to the oscillator 25 to provide an amplitude. -adjustment of the oscillatory displacement generated by it.

In operation, a pair of upper and lower container parts are taken from a stack by a separate device (not shown) and brought by different conveying systems in such a position that a bottom part is located within the tool 23 and an upper part in the top tool 30. The displacement of the carrier 12 and the carrier 14 around the circular heads 13 and 15 provides the vertical displacement between the tools 23 and 30 to bring the container sections close together. When the support assemblies 12 and 14, which run circularly around the heads 13 and 15 as a single unit, have reached a predetermined point with respect to the grooves 19 and 21, the tools 23 and 30 will be closest to each other so that the top and bottom holder sections are also close to each other. Simultaneously with bringing the top and bottom 30 container sections together, air is supplied through the tube 34 to the air oscillator 25, thereby generating a low-frequency oscillation of the upper container located in the tool 30 within the lower container section contained in the tool 23 such that sufficient heat 35 is generated between the two container sections to effect a hermetic bond therebetween.

The number of oscillations necessary to make a connection depends on different parameters and the type of plastic from which the holders 40 are made, as well as the size of the holder 8301424 -5- ♦ and the frequency and amplitude of the oscillations. These will be known to the operator prior to setting the device and the time and frequencies of the oscillations will be preset so that at the time the bond is established the oscillations will be terminated to allow that a good connection is obtained between the container sections. The air oscillator terminates the oscillations in the bottom position such that the container sections will be fully connected to each other. Shortly after the oscillations have ceased and the connection has been made, the displacement of the support assemblies 12 and 14 around the heads 13 and 15, by means of the engagement of the follower rollers 16 and 17 in the grooves 19 and 16, respectively. 21, 15, the support assemblies are vertically spaced to allow removal of the attached container sections. The prepared container will then be removed from the device by known means.

Fig. 5 schematically shows the rotary system to which 20 air supply tubes 33, 34 and 35 are connected. Fig. 5 shows the rotation connection 40 provided with an air outlet 41 connected to the diaphragm supply tube 35, a second air supply opening 42 which can be connected to the air oscillation supply tube 34 and a third air supply opening 43 connectable to the air bearing supply tube 33. When the support assemblies 12 and 14 are rotated about their respective heads 13 and 15, the air supply openings 41-43 communicate with the different supply tubes for supplying a sufficient amount of air to the various air-operated components of the device for a certain period of time.

In this embodiment, the oscillation means includes a pneumatically operated low-frequency oscillator, i.e., an oscillation of about 50 to about 500 vibrations per second. and preferably from 120 to 240 vibrations per sec.

If a higher frequency oscillator is desired, an electrically operated oscillator will be used, with frequencies ranging from about 50 to about 50,000 vibrations per second. and in particular 830 1 42 4 -6- from about 20,000 to 40,000 vibrations per sec.

Fig. 6 shows the second embodiment of the invention, which embodiment is particularly useful for high-frequency oscillation connections of 5 holder parts. In this embodiment, the support assembly of the first embodiment has been replaced by a high-frequency support assembly 100. This support assembly is mounted on corresponding cam track heads 13 and 15 by the follower rollers 17 and 16. The assembly 100 includes an upper support body 101 and a lower roller body 102.

On the upper support body 101 is arranged a console 103 on which there is an ultrasonic transducer 104, which lies in a vertical plane, which is substantially parallel to the cam track head 13. The electrically operated transducer 104 is connected to a power source via electrical connection 105. At the lower end of the converter 104 there is a pin 106, which connects an upper spindle 107 to the converter. An air bearing 108, which is connected to the body 101, supports the spindle 107 in a vertically slidable position. An upper container holding tool 109 is mounted on the lower end of the spindle 107. The tool 109 preferably has an internal cavity which is substantially in the shape of the upper part of the container to be welded. The lower assembly 102 includes a lower spindle 110 mounted on the support block 102 and provided with a holding tool 111 mounted on its top. The tool 111 is provided with an internal cavity, the shape of which corresponds to that of the lower part of the plastic holder to be welded. The tools 109 and 111 have known means for firmly clamping the container sections.

In operation, the two carrier assemblies, which form a single station 100, will be rotated about their respective cam track heads 13 and 15 by the follower rollers 17 and 16, which are received in the grooves 20 and 20, respectively. 21. This twisting movement and the associated movement around the heads 13 and 15 results in a vertical movement of the upper and lower shafts towards and away from each other. At some point of this operation, while the lower and upper tool pins 109 and 111 are spaced apart, plastic retainer parts will be fitted in the tool 109, respectively. in the tool 111 in a known manner. An additional movement of the follower rollers in the grooves serves to bring the top and bottom spindles together until the top and bottom holder sections contact each other. At this time, electrical power will be supplied to the converter through line 105, generating a high-frequency oscillation of the top spindle 10 107, again oscillating the top plastic container relative to the lower plastic container to generate frictional forces in a strong heat development and a consequent welding of the sections together to form a hermetic seal. The continuous displacement of the assembly around the cam track heads then causes the top and bottom spindles to separate, allowing the welded container to be removed from the tools in a known manner.

Fig. 7 schematically shows a rotary connection arranged near the central longitudinal axis of the assembly. In FIG. 7, the power supply circuits are designated 112 and 113. The air supply tube is connected to a rotary air connection 114 to supply air to the air army 108. In addition, known means, such as vacuum or mechanical means, may be provided in the tool holders 109 and 111 to secure the plastic holder sections in place therein during their oscillatory welding.

Fig. 8 schematically shows a top view of a supply system 200 for the welding assembly. The feed assembly includes a rotary feed, such as a star wheel 201, for feeding containers to the different stations 10, and the discharge wheel 202 including a star wheel for removing welded containers after the welding process is completed. The shown welding device 11 comprises ten separate welding stations 10.

Figures 1-3 show various joints that can be welded using the above-described device and rigid plastic container sections. Fig. 8301424 -8- shows a partial cross-section over the top holder section 301 / which is welded to a bottom holder section 302. This type of joint is referred to as a "compression shear" joint. The outer diameter of the lower section 302 is several hundredths of a millimeter larger than the inner diameter of the upper section 301. The section 301 is pushed over the section 302 to obtain an airtight fit and the vibration between the two As a result of the generated frictional heat, sections allow the thermoplastic material to fuse sufficiently to form a hermetic connection between the two parts.

Fig. 2 shows a partial cross-section over a connection between two plastic objects, such as two sections of a container or a container wall and a container bottom. In this connection, the side wall 401 of a container section is oscillated between the upwardly projecting flanges 402 and 403 of a plastic bottom section 404. The wall portion 401 preferably fits somewhat tightly between the top 20 flanges 402 and 403 to provide sufficient frictional heat. to firmly connect the bottom section to the wall 401.

Fig. 3 shows an alternative embodiment of the clamping function of the upper tool 501 of a holder section 502. The holder section 502 must be frictionally welded to the lower holder section 503. In this embodiment, a wedge-shaped clamp 504 connected to a first curve track mounted on an upper curve track head 13, the holding member 502. The element 504 is wedge-shaped at the bottom end and a sliding clamping ring 505 is arranged around the outer circumference of the wedge-shaped clamping member. A second cam track mounted on the top cam track head vertically displaces the clamping member 505 downward on the wedge member 504, providing an inwardly directed compression of the container section 502. The course of the first and the second cam tracks on the top cam track head is such that the element 505 is brought down on the element 504 to compress the container section 502 onto the section 503 after the container section 503 has just entered 8301424 -9- in the flange part 502a. Thereafter, the element 505 is moved downwardly to compress the clamp 504 and the holder section 502 on the holder section 503. After the downward clamping movement of the outer element 505, oscillations are generated throughout the top assembly about the sections 502 and 503 to oscillate and generate enough frictional heat to connect the two sections.

A welding device for friction welding of plastic containers has been described above, which device is particularly suitable for connecting two plastic container sections which have a non-circular cross-section. The present invention uses oscillating axial displacements, in contrast to the known rotary motion of the spin welding devices known to date. The oscillating movement is a translational movement rather than a rotational movement, which allows the holders to be of virtually any cross-sectional shape to be welded together under friction. The present invention describes embodiments for low-frequency oscillation welding of plastic objects and a device for high-frequency oscillation welding.

Although certain embodiments of the present invention have been described and shown in the drawing, it will be clear that the invention is not limited thereto and that many modifications can be made without departing from the inventive idea.

For example, while electrical converters and air-operated oscillators have been described for obtaining the oscillatory welding operation, it will be appreciated that other means such as hydraulic actuation and mechanical oscillations may also be used in their place. While the top holder part is oscillated in contact with the bottom holder part, it is of course also possible to oscillate the bottom part or to oscillate both parts of the holder.

Although the method has been described for welding container parts made of thermoplastic material 40 in general, it will be understood that this can be understood to mean all kinds of different materials, such as styrene resins, polystyrenes, polypropylenes, polycarbonates, polyethylenes, polyethylene terephthalate and polyethylene glycol ref. -talate.

5 conclusions 8301424

Claims (14)

1. Device for frictional welding of two thermoplastic objects, characterized in that the device comprises: a first holder suitable for clampingly receiving a first object to be welded, orat first clamping means and a holder for receiving the first an object, which holder is mounted on a tool suitable for axial displacement, whose tool is slidably mounted on a first pedestal; oscillating means connected to the first tool and to the first pedestal and arranged to oscillate the first tool axially with respect to the first pedestal; a second holder mounted on a second pedestal and adapted to clampingly receive a second object to be welded to the first object, the second holder being axially aligned with the first holder and close to it and comprising a cavity for receiving the second object and second clamping means for holding the second object in the second holder; and means for moving the first and second containers toward and away from each other between an article receiving position and an article dispensing position. 2. Device as claimed in claim 1, characterized in that the displacing means consist of roll-tracking means rotatably mounted on the pedestal and curve means arranged in a base station and suitable for receiving the follower rollers for providing an axial displacement of the holders. 30 Device according to claim 1 or 2, characterized in that the oscillating means consist of a pneumatically operated low-frequency oscillator suitable for a range of 50 to about 500 vibrations per second. in particular 120 to 240 vibrations per sec. 4. Device according to claim 1 or 2, characterized in that the oscillating means consist of an electrically operated oscillator suitable for about 50 to about 50,000 vibrations per second, in particular 20,000 to 40,000 vibrations per second. 5. Device as claimed in any of the foregoing claims, characterized in that the clamping means in each container comprise vacuum means in the containers. 6. Device according to any one of the preceding claims, characterized in that the oscillating means comprise means for varying the frequency and means for varying its amplitude. Friction welding device provided with a number of stations as described in any one of the preceding claims, characterized in that the assembly comprises: a stationary foot part; an upper assembly mounted on the foot portion; a lower assembly mounted on the foot portion below the upper assembly; Which top and bottom assemblies are adapted to align with each other over the circumference of the foot portion; wherein at least one of the top and bottom assemblies are axially displaceable relative to the other assembly on the foot portion and means are provided for displacing at least one of the top and bottom assemblies axially relative to the other assembly; force means for applying operating power to the oscillation means and the holder means at the welding stations, said displacement means being adapted to move the first holder back and forth between a first position in which the thermoplastic objects are spaced from one another and a second position in which the thermoplastic objects are arranged telescopically with respect to each other, the oscillation means being suitable for oscillating only when the first and second holding means are in the position where the objects are arranged together while the oscillation means further means for adjusting the frequency and the amplitude of the os-5 oscillating action to keep the thermoplastic objects in telescopic engagement with each other during their oscillation. 8. Device as claimed in claim 7, characterized in that the top and bottom assemblies are rotatably mounted on the stationary foot part and in that the displacing means comprise curve means on the foot part and curve follow means on at least one of the top and bottom assemblies. 15 9. Device according to claim 7 or 8, characterized in that means are provided for supplying thermoplastic objects to the welding stations and means for removing welded thermoplastic objects. the welding stations. 10. Method for welding at least two correspondingly shaped thermoplastic parts together, which parts are provided with closely fitting complementary connecting parts, characterized by: telescoping the closely fitting parts of the objects; oscillating the parts axially relative to each other at a sufficient speed and for a sufficient period of time to generate enough heat to cause melting of the contact areas; and bringing the sections to a final desired position and allowing the heated areas to cool thereby welding the sections together. 35 Method according to claim 10, characterized in that a container is formed from two thermoplastic sections each with a non-circular cross-section, each section being clamped in a container, the two sections being axially aligned and 8301424 -14- telescoped together. 12. A method according to claim 10 or 11, characterized in that the sections of corresponding shape are manufactured from crystalline or amorphous, corresponding or different plastic materials, in the case of different plastic materials the melting temperatures not more than about 15 ° C are different from each other and which materials are selected from the group consisting of styrene resins, polystyrenes, polypropylenes, polycarbonates, polyethylenes, polyethylene terephthalate and polyethylene glycol terephthalate. 13. A method according to any one of claims 10-12, characterized in that the oscillation phase is performed with a frequency of about 50 to about 50,000 vibrations per second. 14. Device and method for welding together thermoplastic objects as described and / or shown in the drawing. 8301424