Ultrasonic device for a polymer extruder machine

Abstract

An ultrasonic device comprising a chamber (10) provided with an inlet bore (11), which receives a melted pressurized polymer, an outlet bore (12) and a sonotrode housing bore (13) through which a distal portion (21) of an ultrasonic head (20) is inserted into the chamber, wherein the distal portion is separated from the rest of the ultrasonic head by a first nodal plane (PN1) wherein there is a first surface (S1) in contact with a complementary surface of a ring seal (30) that closes the chamber, and wherein the ultrasonic head includes a second nodal plane (PN2) away from and parallel to the first nodal plane (PN1) coinciding with or adjacent to a second surface (S2) wherein an anchoring device (40) presses the ultrasonic head against the ring seal ensuring a tight closure.

Claims

1. An ultrasonic device for a polymer extruder, the ultrasonic device comprising: a chamber configured to retain a melted pressurized polymer comprising an inlet bore operatively connected to a polymer extruder apparatus configured to feed the melted pressurized polymer into the chamber through the inlet bore, an outlet bore configured to extrude the melted pressurized polymer, and a sonotrode housing bore, an ultrasonic head comprising a distal portion substantially defined by the at least one sonotrode and disposed in the chamber through the at least one sonotrode housing bore and projecting in cantilever into the chamber, and a proximal portion separated from the distal portion by a first nodal plane; the distal portion is configured to remain in contact with the melted pressurized polymer contained in the chamber, the proximal portion is configured to remain outside the chamber and in connection with an ultrasonic transducer, the proximal portion comprising at least a second nodal plane disposed away from and parallel to the first nodal plane; a ring seal disposed in contact with the ultrasonic head and coincident with the first nodal plane, the ring seal configured to seal the at least one sonotrode housing bore of the chamber that contains the melted pressurized polymer; the first nodal plane being coplanar with a first surface of the ultrasonic head, the first surface being annular, and with a first annular surface of the ring seal disposed parallel to the first surface of the ultrasonic head; the second nodal plane being coplanar with a second surface of the ultrasonic head and parallel to the first surface of the ultrasonic head, an anchoring device being attached to the second surface of the ultrasonic head, a pressure device connected at least to the anchoring device and configured to apply a pressure in a direction perpendicular to the first surface of the ultrasonic head compressing at least part of the proximal portion between the anchoring device and the ring seal, the pressure device further configured to transmit pressure to the ring seal producing a tight seal around the chamber.

2. The ultrasonic device according to claim 1, wherein the proximal portion of the ultrasonic head is at least partially defined by an ultrasonic amplifier disposed between the at least one sonotrode and the ultrasonic transducer.

3. The ultrasonic device according to claim 2, wherein the second nodal plane is disposed away from the joint between the at least one sonotrode and the ultrasonic amplifier.

4. The ultrasonic device according to claim 1, wherein substantially the entire proximal portion of the ultrasonic head is defined by the at least one sonotrode.

5. The ultrasonic device according to claim 1, wherein the distal portion of the ultrasonic head comprises a smaller diameter than the proximal portion of the ultrasonic head.

6. The ultrasonic device according to claim 5, wherein a transition between the distal portion of smaller diameter and the proximal portion of larger diameter substantially defines the first surface of the ultrasonic head.

7. The ultrasonic device according to claim 1, wherein the chamber is provided with a third surface, which is annular, disposed around the at least one sonotrode housing bore opposite to the first surface of the ultrasonic head, the third surface of the ultrasonic head being in contact with a second surface of the ring seal; the ring seal comprising a tubular body retained between the first surface and the third surface of the ultrasonic head.

8. The ultrasonic device according to claim 7, wherein the third surface of the ultrasonic head defines an annular seat configured to provide a substantially precise positioning of the ring seal.

9. The ultrasonic device according to claim 7, wherein the ring seal is a metallic or a ceramic ring seal.

10. The ultrasonic device according to claim 7, wherein the ring seal defines an inner gap with a larger cross section than the cross section of the distal portion of the at least one sonotrode.

11. The ultrasonic device according to claim 1, wherein the pressure device comprises a plurality of connectors, each one of the plurality of connectors attached on one end to the anchoring device and on another end to a body containing the chamber.

12. The ultrasonic device according to claim 1, wherein the pressure applied by the pressure device is greater than the pressure of the melted polymer of the chamber.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The foregoing and other advantages and characteristics will be more completely understood from the following detailed description of an exemplary embodiment with reference to the attached drawings, which must be taken by way of illustration and not limitation, wherein:

(2) FIG. 1 shows a schematic cross section of the ultrasonic device wherein the polymer extruder apparatus is not shown but wherein the direction in which the melted polymer is displaced from said extruder apparatus to the outlet bore is indicated, by means of an arrow, shown in a simplified way; and

(3) FIG. 2 shows the same ultrasonic device of FIG. 1 but in an exploded view.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

(4) The attached figures show exemplary embodiments with an illustrative non-limiting character of the present invention.

(5) According to a preferred embodiment, the proposed ultrasonic device will be specially adapted for its use in a polymer extrusion machine (with or without additives).

(6) Said extruder includes a polymer extruder apparatus that pressurizes the melted polymer into the chamber 10 through an inlet bore 11. Said chamber will be provided, in addition to inlet bore 11, with a sonotrode housing bore 13 and with an outlet bore 12 connected to a forming die that determines the geometry of the extruded polymer product produced by said extruder apparatus.

(7) The inlet 11 and outlet 12 bores may be aligned or not aligned.

(8) The polymer extruder apparatus includes, in this example, a cylindrical fusion chamber, which contains one or two spindles and a granular polymer inlet at the beginning of the cylindrical fusion chamber, although other embodiments are also contemplated. In the apparatus of this type, the rotation of the spindles compresses the polymer, conveys, kneads and mixes it with additives, if there are any, being also capable of including heaters that increase the temperature of the polymer to favour its melting. The melted polymer flow is introduced in the chamber that contains the distal portion of the ultrasonic head through an inlet bore 11.

(9) Said chamber containing the distal portion of the ultrasonic head may be connected, through the inlet bore, at the end of the extruder apparatus, or, on the contrary, may be integrated in an intermediate portion of said extruder apparatus, such that the vibration produced by the ultrasonic head will be applied to the polymer contained in the extruder apparatus. In such an embodiment, the spindle, or the spindles, will preferably go through said chamber, although it is also contemplated that one or two spindles may be located before and one or two after said chamber.

(10) The proposed ultrasonic device is formed by a vibration-generating ultrasonic transducer 25 in connection with an ultrasonic head 20 to which it transmits the generated vibration.

(11) Said ultrasonic head 20 will be formed, in turn, by an ultrasonic amplifier 24 in direct contact with the ultrasonic transducer 25, and by a sonotrode 23 connected to said ultrasonic amplifier 24.

(12) A distal portion 21 of the ultrasonic head 20, corresponding to a portion of the sonotrode 23, will be contained within the chamber 10 inserted projecting in cantilever into it through the sonotrode housing bore 13, said distal portion 21 remaining in contact with the pressurized melted polymer to which vibration is applied modifying its properties before exiting through the outlet bore 12 of the chamber.

(13) The rest of the ultrasonic head 20 constitutes a proximal portion 22 that remains outside the chamber 10.

(14) The ultrasonic transducers 25 typically generate a vibration in the shape of a sinusoidal wave that spreads in the ultrasonic head 20 in the shape of a stationary wave. Any body subjected to a stationary wave generates one or several nodal planes wherein the vibration amplitude will be zero at all times.

(15) The proposed ultrasonic head 20 will be configured so that a first nodal plane PN1 is defined between the distal portion 21 and the proximal portion 22. This allows that, in correspondence of said first nodal plane PN1, a ring seal 30 may be arranged around the ultrasonic head 20, and in contact therewith, thus sealing the sonotrode housing bore 13, keeping the melted pressurized polymer contained in the chamber 10 from flowing towards the outside the chamber 10 therethrough.

(16) Said ring seal 30 could affect the vibration of the ultrasonic head 20, or said vibration could affect the sealing produced by the ring seal 30. For this reason, it is proposed that the ring seal 30 consists of a tubular body through which the distal portion 21 of the ultrasonic head 20 is inserted, said tubular body being provided with an annular surface of the ring seal 30 parallel and coplanar to the first nodal plane PN1 of the ultrasonic head 20. The ultrasonic head 20 is also provided with a first annular surface S1 coplanar with the first nodal plane PN1 complementary with the annular surface of the ring seal 30.

(17) In an assembled position, the ultrasonic head 20 is arranged with its first annular surface S1 resting on and in contact with the annular surface of the ring seal 30.

(18) Said surfaces being coplanar with the first nodal plane PN1, the vibration amplitude on all points of said annular surface will be equal to zero, so that the sealing produced between both will not be affected by the vibration of the ultrasonic head 20.

(19) The ultrasonic head 20 will also be configured to generate, in its proximal portion 22, a second nodal plane PN2 parallel to and separated from the first nodal plane PN1. Preferably, said second nodal plane PN2 will be away from the joint between the sonotrode 23 and the ultrasonic amplifier 24, to avoid subjecting said joint to excessive stresses that may damage the joining means, such as, for example, a threaded joint.

(20) The ultrasonic head 20 will also be provided with a second surface S2 parallel to the first surface S1 and coplanar or adjacent to the second nodal plane PN2, such that the vibration amplitude in the second surface S2 will be zero or highly reduced.

(21) The second surface S2 may be formed by multiple second partial surfaces, all of them coplanar to each other, forming an annular discontinuous surface, without this affecting the invention.

(22) An anchoring device 40, which in this embodiment it is proposed to be a flat plate provided with a central through hole through which part of the ultrasonic head 20 goes, is placed resting on and in contact with the second surface S2, the periphery of said central hole remaining in contact with the second surface S2 of the ultrasonic head 20.

(23) A pressure device 41 applies pressure to said anchoring device 40 in a direction perpendicular to the first and second nodal planes PN1 and PN2, which is transmitted to the ultrasonic head 20 through the second surface S2, compressing part of the ultrasonic head 20 against the ring seal 30, thus ensuring that the pressure of the melted polymer contained in the chamber 10 does not causes leaks through the joint of the ring seal 30 with the first surface S1 of the ultrasonic head 20. The pressure applied by the pressure device 41 will be greater than the pressure of the melted polymer of the chamber 10.

(24) The arrangement of the first surface S1 and the geometry of the ring seal 30, together with the compression direction applied on the ultrasonic head 20, produces a sealing between the ultrasonic head 20 and the ring seal 30 in an axial direction of said ultrasonic head 20, instead of in a radial direction, as is common in the art.

(25) In the present embodiment, the pressure device 41 consists of at least two bars parallel to each other and perpendicular to the first and second nodal planes PN1 and PN2 of the ultrasonic head 20 that have an end attached to a body that contains the chamber 10 and an end that traverses through holes of the anchoring device 40, allowing for the guidance of the anchoring device in an axial direction defined by the bars.

(26) Said bars will preferably be threaded bars and will be provided with a number of nuts as a tightening device 42 that will allow to shift the anchoring device 40 towards the body that contains the chamber 10 compressing the sandwiched ultrasonic head 20. Alternatively, it is contemplated that the threaded bars may rotate, driven by a motor, for example, the nuts being attached to or integrated in the anchoring device 40.

(27) It is also proposed that the ring seal 30 be an independent piece of the body that contains the chamber 10, thus facilitating its maintenance and replacement. In such a case, the body that contains the chamber 10 will be provided, around the sonotrode housing bore 13, with a third surface S3 parallel and opposite to the first surface S1 of the ultrasonic head 20, and the ring seal 30 will also have an annular flat surface configured to remain seated on the third surface S3, retaining the ring seal 30 between the ultrasonic head 20 and the body that contains the chamber 10. The pressure applied by the pressure device ensures that both gaskets of the ring seal 30 are sealed, avoiding the ejection of the melted polymer.

(28) It will be understood that the different parts that constitute the invention described in an embodiment may be freely combined with the parts described in other different embodiments even if such a combination has not been explicitly described, provided that no prejudice exists in the combination.