MXPA00003148A - Hollow vibrational horn - Google Patents

Abstract

The horn (10) includes an outer cylinder (12) and an inner shaft (18) connected by a disk (20). The shaft has an axial input end (22), and receives vibrational energy at the axial input end and transmits the vibrational energy to the cylinder. The cylinder is hollow and has an inner surface (26), an outer surface (28), and first and second opposing end surfaces (30, 32). The second end surface serves as a welding surface which applies vibrational energy to an object. The welding surface moves with the application of vibrational energy to the input end of the shaft. The disk portion connects the inner shaft to the cylinder and transmits the vibrational energy from the inner shaft to the cylinder.

Description

HOLLOW VIBRATIONAL HORN TECHNICAL FIELD The present invention relates to vibrational bodies. More particularly, the present invention relates to ultrasonic welding horns.

BACKGROUND OF THE INVENTION Ultrasonic welding is a critical process for making facial masks. For most of the masks, a filter medium in the form of a receptacle is attached by ultrasonic welding to a substrate or cover. The welding is done around the outer periphery with a desired pattern. Depending on the product requirements and process conditions, various patterns are used, including the grid pattern, the peripheral weld pattern and the eyebrow pattern, which are shown in Figures IA, IB and 1C. In some cases the patterns are used for cutting and sealing operations. A common feature in all patterns is that the internal diameter is greater than 7-10 cm (3-4 inches). The horns currently used for ultrasonic welding face masks generally have a diameter REF .: 33143 outside of 15 cm (6 inches). The horn is formed with multiple grooves machined radially through the center, as shown in Figure 2. The grooves are designed to control the amplitude profile of the horn on the welded surface. Without the slots, the amplitude varies greatly over the welded surface. In some cases, the welding amplitude at certain positions is zero and no welding occurs at those positions. This slotted horn is used to perform peripheral welding of facial masks and adhesion of the layers. A pattern is usually machined on the end of the horn opposite the input or excitation end. This design is very complicated to machine, and has proven to be unreliable in production. This has resulted in significant costs for the production of available horns, and in an excess of idle machinery time. In addition, the amplitude of vibration on the welded surface varies 25-30% along the welded pattern. In order to obtain acceptable welds with this lack of uniformity, the waiting time of the welding process must be increased, resulting in reduced performance of the entire machine. The lack of uniformity can result in some parts being brazed and poor welding in others. This reduces the process interval. For some products which contain thicker layers or increased number of layers, higher welding amplitudes are required. In such cases, this horn is limited, because the higher amplitudes cause a rapid failure. In addition, the grooves increase the stresses in the horn and it is likely that the horn will fail in these slot positions. Other designs are available such as the "bell-shaped" horn with or without grooves, as shown in figure 3. None of these designs has been shown to be fully acceptable due to displacement of lack of uniformity, amplitude restrictions or premature failure. .

BRIEF DESCRIPTION OF THE INVENTION A vibrational horn is provided to impart energy at a selected wavelength, • frequency and amplitude, which includes an axis, a cylinder and a portion of the disk that connects the shaft and the cylinder. The shaft receives vibrational energy at one axial input end and transmits the vibrational energy to the disk portion. The disk portion transmits the vibrational energy to the cylinder.

The cylinder has an inner surface, an outer surface, and first and second opposing end surfaces.

The axis is located adjacent to the first end surface, and the second end surface serves as a welding surface which applies vibrational energy to an object. The cylinder is hollow and has an outside diameter which is greater than the diameter of the shaft. The welding surface moves as the cylinder expands and contracts with the application of vibrational energy to the input end of the shaft. The cylinder can be a straight circular cylinder or it can have an elliptical diameter or it can be rectangular or in any of many other ways. The length of the cylinder can be a multiple of about half the wavelength of the horn material. In a modality, the axis is coaxial with the cylinder. The horn may be an ultrasonic horn with the welded surface moving substantially in phase with the movement of the axial entry end of the horn. In one modification, the disk portion has a hollow portion on the oriented side away from the welding surface to improve the bending of the cylinder. In another modification, the shaft has a notch formed in the axial output end to minimize the voltage for a given operating amplitude. In another modification, the cylinder has a cut in the inner surface to control the displacement along the welding surface. In another modification, the cylinder has a cutout on the outer surface to obtain the desired amplitude profile along the welding surface.

BRIEF DESCRIPTION OF THE DRAWINGS Figures IA, IB, and 1C show various soldier patterns. Figure 2 is a perspective view of a known slotted ultrasonic horn. Figure 3 is a cross-sectional view of a known bell-shaped horn. Figure 4 is a cross-sectional view of the ultrasonic horn of the present invention. Figure 5A is a cross-sectional view of the out-of-phase movement of a known bar horn. Figure 5B is a cross-sectional view of the in-phase movement of the horn of Figure 4. Figure 6 is a cross-sectional view of another embodiment of the ultrasonic horn of the present invention. Figure 7 is a cross-sectional view of another embodiment of the ultrasonic horn of the present invention.

DETAILED DESCRIPTION The ultrasonic welding horn of this invention can be used to join multiple layers of face masking material. Although the horn is designed for penetrating welding of a face mask, it can be used to weld other materials such as molded plastic parts, plastic films and non-woven materials to make many other products. In addition, this horn can be used with other welding processes, such as scanning welding, which can be easily adapted due to the uniformity of the displacement of the welding surface and the simplicity of the design. The size of the horn can be increased or decreased with minimal design effort, and a very shallow welding pattern can be machined on the welding surface. This horn acquires more uniform and greater amplitudes, with lower tensions and can have a larger diameter than the known horns. The larger and more uniform amplitudes require less welding time, which results in a higher machine speed, - a wider process range and the ability to weld thicker layers and increased numbers of layers. The reduced tension increases the reliability of the horn and reduces the idle time of the machine. A larger diameter horn accommodates larger weld patterns and provides greater options for product improvement and development. Figure 4 shows an embodiment of the ultrasonic horn of the invention. The horn imparts energy at a selected wavelength, frequency and amplitude. The horn 10 is a hollow cylinder 12 with an inner diameter 14, in the illustrated embodiment, of 10 cm (4 inches) and with an outer diameter 16 of 16.26 cm (6.4 inches). This design acquires an acceptable uniform amplitude at all points between the inner and outer diameters 14, 16 on the weld face. Therefore, any shallow machined pattern on this weld face will show a uniform amplitude. For patterns whose depth is small compared to the length of the horn, additional material can be provided to machine the pattern. The total length of the horn is a multiple of about half the wavelength of the horn material. The horn can be made of aluminum, titanium, steel or other materials. The dimensions of the horn depend on the wavelength of the material used to obtain the length requirement of half the wavelength. Although the horn 10 is shown as a single part, conceptually it includes an outer cylinder 12 (having diameters 14, 16, inner and outer) and an inner shaft 18 connected by a disc 20. The shaft 18 can have any shape. The most common form is a cylindrical shaft. The shaft 18 has an axial inlet end 22 and an axial outlet end, and receives vibrational energy at the axial inlet end and transmits the vibrational energy at the axial outlet end. The axial output end is not a defined surface of the shaft 18. It is generally considered to be the area where the shaft 18 connects to the disk 20. The cylinder 12 can be a straight circular cylinder, may have an elliptical diameter or may have other shapes, such as polygonal, (such as triangular, rectangular, pentagonal, etc.), and combinations of two or more shapes. It can be concave or convex. The cylinder 12 is hollow and has an inner surface 26 having the inner diameter 14, an outer surface 28 having an outer diameter 16, a first and second surfaces 30, 32 of opposite end. The axis 18 is located adjacent to the first end surface 30 (connected by disk 20), and second end surface 32 serves as a welding surface which applies vibrational energy to an object. The welding surface 32 moves as the cylinder 12 expands and contracts with the application of vibrational energy to the input end 22 of the shaft 18. The shaft 18 can be coaxial or eccentric with the cylinder 12. A hole 24 tapered on the cylinder 12 provides attachment to a reinforcement (not shown) using a threaded rod (not shown), In an alternative embodiment, both end surfaces 30, 32 can serve as welding surfaces. The disk portion 20 connects the inner shaft 18 to the cylinder 12 and transmits the vibrational energy from the inner shaft to the cylinder. As shown, the disk 20 may be circular although it may have other shapes depending on the shape of the horn. In alternative embodiments, the disk portion 20 need not be located adjacent to the first end surface 30 of the cylinder 12. The disk portion can be located in any axial position with respect to the cylinder 12. Adjust the position of the disk portion 20 it can be used to change the gain of the horn (the ratio of the amplitudes of output to input) and the amplitude profile on the welded surface 32. If the disk portion 20 is located centrally, the cylinder 12 can have both surfaces 30, 32 functioning as welding surfaces. In one version, as shown in Figure 4, the disk portion 20 may optionally have an annular hollow portion 34 on an oriented side away from the welding surface 32 to improve the flexing of the disk 20. In addition, the shaft 18 optionally it may have a notch 36 formed in the axial outlet end to minimize the tension for a given vibration mode. The notch 36 may extend over the entire circumference of the horn or only in one part. In a conventional bar or cylinder horn having a length constituting an odd integer multiple of about half the wavelength of the material, as shown in Fig. 2, the in and out shifts are "out of phase "180 degrees. In other words, if the acting surface (a reinforcement mounting surface) moves inward towards the center of the horn, the lower welding surface also moves inwardly, as shown in Figure 5A and vice versa. In Figure 5A, the dashed line shows the undeformed shape of the horn and the solid line shows the deformed shape. If the downward movement of the acting surface is considered negative, then the upward movement of the welding surface is positive. Therefore, the movement between the acting surface and the welded surface is of opposite sign and is considered to be out of phase by 180 degrees. In the present invention, the vibration mode is opposite to the conventional horn. For example, consider a half-wavelength horn, shown in Fig. 4, with a length L. As the acting surface, the input end 22 moves downwardly, the welding surface 32 is also moves in a descending manner, as shown in Figure 5B. The displacement of the input end 22 and the welding surface 32 are in the same direction and therefore the movement is identified as "in phase". The cylinder 12 acts as a bar horn because the opposite ends 30, 32 are out of phase. In each cycle of vibration, the outer cylinder 12 advances through compression and tension. The cylinder 12 is coupled to the shaft 18 by the disc 20. Therefore, in each vibration cycle, the disc 20 advances through the bending movement and undergoes compression and tension stresses. In a conventional bar or cylinder horn having a length that is a whole integer multiple of about half the wavelength of the material, the entrance and the exit are "in phase". In other words, if the acting surface (a reinforcement mounting surface) moves inward toward the center of the horn, the lower welding surface moves outward, and vice versa. In the present invention for the horn of the same approximate length L, the inlet and outlet are "out of phase". As the acting surface, the inlet end 22 moves downward, and the welding surface 32 moves upwardly. The displacement of the inlet end 22 and the welding surface 32 are in opposite directions and the movement is "out of phase". Another difference between the horn 10 of the invention and the horn of Figure 2 or Figure 3, is that the entire horn of Figure 2 acts as a semi-wavelength bar horn with the input surfaces and of output acting axially in all points. In the horn 10 of the present invention, only the outer cylinder 12 acts as a semi-wavelength bar horn with the inlet and outlet surfaces acting axially.

The amplitude profile of the welding surface 32, the gain in the horn 10, the reasoning frequency and the tension in the horn are functions of the inner diameter 14, the external diameter 16, the thickness and the axial position of the disc 20, the length of the horn 10, the depth of the hollow 34 and the notch 36, and the material used for the horn 10. Various variations can be made to this basic configuration to alter gain, tension, uniformity of amplitude and natural frequency. For example, the corners of the cylinder 12 on the first surface 30 may be bevelled. The disk portion 20 can extend beyond the outer diameter of the cylinder 12. The cylinder 12 can extend beyond the disk portion 20 for all or a portion of the first surface 30. Another design variation of the hollow vibrational horn is shown in figure 6, which has an outer diameter of 20 cm (8 inches) and an inner diameter of 10 cm (4 inches). In the horn 10 'of Figure 6, all the characteristics of the horn 10 are the same. To control the displacement along the welding surface 32, a cut-out 38 is made on the inner surface 26 of the cylinder 12. A similar cut-out 40 can be provided on the outer surface 28, if required, to obtain the profile amplitude that is desired along the welding surface 32. The placement, depth and width of the cutouts 38, 40 directly alters the amplitude profile on the welding surface 32. In addition, the cutouts 38, 40 can extend completely around the cylinder 12 or partially around the cylinder. Optionally, a cover 42 can be placed through the second end surface 32 of the cylinder 12, as shown in Figure 7. The cover 42 can serve as a larger welding surface while the horn still functions as a horn hollow, as described above. A major advantage of the design of the new hollow horn, in comparison with the known horns, is that it has a better uniformity of displacement or a controlled displacement profile. Both measurements and in finite element analysis have shown that a displacement variation of less than 5% is obtained. - Better uniformity means that the waiting time for a penetrating welding operation can be reduced, leading to improved performance for the welding operation, and often improved operation for the entire production machine. Better uniformity also provides a uniform weld and improved performance with a wider process range. The hollow horn of this invention also has a lower internal tension. When internal stresses are reduced, the horn can withstand a greater number of cycles before it fails. This leads to less waste of the machine and reduces maintenance costs because each horn has a longer life. In addition, lower internal stresses allow the horn to obtain a greater horn amplitude. A horn with a high amplitude can be used for processes that are not feasible with a horn of smaller amplitude, such as a thick layer or multi-layered networks for facial masks. The hollow horn is simple to machine. Simple machining will reduce manufacturing costs. This horn can be cheaper to process than the existing horn. In addition, the hollow horn has a larger diameter. It can accommodate larger welded patterns, more options for product modifications and new developments.

EXAMPLE The horn of figure 4 of aluminum 7075-T651 is made and its welding frequency is measured, which is 20.09 kHz. The gain is approximately 1.2. The output amplitude at the welding surface of the horn is measured when the horn is excited under different reinforcements, as shown below.

Reinforcement ratio Outer amplitude, thousandths p-p 0. 67: 1 0.41 1.50: 1 1.4 2.50: 1 2.0 3.75: 1 * 3.5 * This reinforcement is actually a combination of 1.5: 1 and 2.5: 1 reinforcements in series. In all test cases, the power drawn by the horn in air for the power supply is less than 50 watts, and the horn shows no signs of warming. The other modes of horn vibration occur at 18.3 and 21.5 kHz, and are far apart from the operating frequency of 20.09 kHz. The uniformity of the amplitude along the weld surface is measured and is within 5%. The grid pattern shown in Figure IA applies to another horn with the dimensions as shown in Figure 4, except for the total length. In order to adapt this pattern, the cylinder length is increased by extending the weld surface down by 0.25 cm (0.1 inch) which is equal to the depth of the pattern. The frequency of this horn before machining the pattern is 19.85 kHz. After the grid pattern has been machined, it is determined that the welding frequency is 20.01 kHz.

In comparison, a horn of Figure 2 is made with the eyebrow pattern of Figure 1C and installed on a production machine. This horn fails frequently and is not reliable. In some cases, the horn fails immediately and in some cases after welding 500 parts. The hollow horn in this example welds at least 25,000 parts before failing. Because of the uniformity of amplitude, there is increased performance in the welding process and it has an extended process interval. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (9)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A vibrational horn for imparting energy at a selected wavelength, frequency and amplitude, wherein the horn comprises: an axis having an axial input end, wherein the shaft receives vibrational energy at the axial input end; a cylinder having an inner surface, an outer surface, and first and second opposing end surfaces, wherein the axis is located adjacent to the first end surface, and the second end surface serves as a welding surface which applies vibrational energy to an object, where the cylinder is hollow and has an outside diameter which is greater than the diameter of the shaft, and where the surface of the weld moves as the cylinder expands and contracts with the application of energy vibrational to the input end of the shaft; and a disk portion connecting the inner shaft to the cylinder, wherein the shaft transmits the vibrational energy to the portion of the disc and the disc portion flexibly transmits the vibrational energy to the cylinder, where regardless of whether the length of the cylinder is a An odd integer multiple or pair of about half the wavelength of the horn material, the first end surface of the cylinder moves out of the base with the movement of the axial inlet end of the horn.

2. The horn according to claim 1, characterized in that the length of the cylinder is an odd integer multiple of about half the wavelength of the horn material, wherein the first end surface of the cylinder moves out of phase with the movement of the second end surface, and wherein the welding surface moves substantially in phase with the movement of the xial entry end of the horn.

3. The horn according to claim 1, characterized in that the length of the cylinder is an even integral multiple of about half the wavelength of the horn material, wherein the first end surface of the cylinder moves in phase with the movement of the horn material. of the second end surface, and wherein the welding surface moves substantially out of phase with the movement of the axial inlet end of the horn.

4. The horn according to claim 1, characterized in that the cylinder is of a circular, elliptical, polygonal shape or a combination of these forms.

5. The horn according to claim 1, characterized in that the axis is coaxial with the cylinder.

6. The horn according to claim 1, characterized in that the disk portion has a recess on the oriented side away from the welding surface to improve the deflection of the disk.

7. The horn according to claim 1, characterized in that the shaft has a notch formed in the axial outlet end to minimize the tension for a given vibration mode.

8. The horn according to claim 1, characterized in that the cylinder has cutouts on at least one of: the inner surface to control the displacement along the welding surface and the outer surface to obtain the desired amplitude profile at the length of the welding surface.

9. The horn according to claim 1, characterized in that it further comprises a cap positioned through the second end surface of the cylinder to serve as a larger welding surface while the horn still operates as a hollow horn. HOLLOW VIBRATIONAL HORN SUMMARY OF THE INVENTION The horn (10) includes an outer cylinder (12) and an inner shaft (18) connected by a disc (20). The shaft has an axial input end (22) and receives vibrational energy at the axial input end, and transmits vibrational energy to the cylinder. The cylinder is hollow and has an inner surface (26), an outer surface (28) and a first and second opposed end surfaces (30, 32). The second end surface serves as a • welding surface which applies vibrational energy to an object. The welding surface moves with the application of vibrational energy to the input end of the shaft. The disk portion connects the inner shaft to the cylinder and transmits the vibrational energy from the inner shaft to the cylinder.