CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No. 62/567,313 which was filed on October 3, 2017, and is incorporated herein by reference.

BACKGROUND

[0002] Ultrasonic welders are commonly used to weld plastic components to one another. A workpiece comprising multiple components are arranged on a support structure or fixture. The components are clamped in place under pressure applied by a horn. The horn is excited at high frequencies by a converter, which generates sufficient heat between the components to melt the materials together.

[0003] During use in a production environment, the horn heats up particularly with short cycle times. The frequency of the heated horn will drift outside of its desired high frequency needed for welding. In addition, elevated horn temperatures can cause loose welds due to improper forming of the molten plastic. To address this problem, the horn may be cooled, for example, by directing cooling air onto the horn. One typical arrangement uses a conduit arranged outside of the ultrasonic welding assembly with an end of the conduit directed at an exterior of the horn. In a production environment, this conduit may become bent or damaged.

[0004] Another horn cooling arrangement has been proposed in which air is introduced into the side of the horn through a hole at the exterior of the horn's base. This additional structure on the horn will be subject to vibrations and undesired strain during welding operations. The external plumbing may also unpredictably affect the frequency at which the horn vibrates.

SUMMARY

[0005] In one exemplary embodiment, an ultrasonic welder includes a converter having an end. A first cooling passage portion extends from the converter through to the end. A horn is mounted to the converter at the end. The horn has a second cooling passage portion in fluid communication with the first cooling passage portion. [0006] In a further embodiment of the above, the converter includes a housing that has a mounting block and a cavity. A piezoelectric assembly is arranged in the cavity and clamped to the mounting block. The mounting block provides the end.

[0007] In a further embodiment of any of the above, the piezoelectric assembly includes a hole that receives a fastener that secures the piezoelectric assembly to the mounting block. The fastener provides the first cooling passage portion in fluid communication with the cavity.

[0008] In a further embodiment of any of the above, the housing has an inlet in fluid communication with the cavity. The inlet is configured to receive pressurized fluid from an air source.

[0009] In a further embodiment of any of the above, the piezoelectric assembly includes multiple piezoelectric elements arranged in a stack. A pressure plate is provided on the stack opposite the mounting plate. The fastener extends through the pressure plate and the stack.

[0010] In a further embodiment of any of the above, the horn includes a neck extending from a base that has a mounting surface abutting the end. A fastening element secures the base to the end. The fastening element provides the second cooling passage portion.

[0011] In a further embodiment of any of the above, the fastening element may be a stud.

[0012] In a further embodiment of any of the above, the second cooling passage portion extends from the fastening element toward a working surface that is provided on a terminal end of the neck opposite the base.

[0013] In a further embodiment of any of the above, an exit is provided in the neck and in fluid communication with the second cooling passage portion.

[0014] In a further embodiment of any of the above, the base is free from any cooling holes exiting an exterior surface of the base that are in fluid communication with the second cooling passage portion.

[0015] In another exemplary embodiment, an ultrasonic horn includes a neck extending from a base to a terminal end that provides a working surface. The base provides a mounting surface that includes a fastening element. A cooling passage extends from the neck to a fastening element terminal end. The cooling passage is configured to receive cooling fluid at the fastening element terminal end.

[0016] In a further embodiment of the above, the fastening element may be a stud.

[0017] In a further embodiment of any of the above, an exit is provided in the neck adjacent to the working surface and in fluid communication with the cooling passage.

[0018] In a further embodiment of any of the above, the base is free from any cooling holes exiting an exterior surface of the base that are in fluid communication with the second cooling passage portion.

[0019] In another exemplary embodiment, an ultrasonic converter includes a housing having a mounting block and a cavity. A cooling passage extends from the converter through to the mounting block. A piezoelectric assembly is arranged in the cavity and clamped to the mounting block. The mounting block provides the end configured to be secured to a horn.

[0020] In a further embodiment of any of the above, the piezoelectric assembly includes a hole that receives a fastener that secures the piezoelectric assembly to the mounting block. The fastener provides the cooling passage in fluid communication with the cavity.

[0021] In a further embodiment of any of the above, the housing has an inlet in fluid communication with the cavity. The inlet is configured to receive pressurized fluid from an air source.

[0022] In a further embodiment of any of the above, the piezoelectric assembly includes multiple piezoelectric elements arranged in a stack. A pressure plate is provided on the stack opposite the mounting plate. The fastener extends through the pressure plate and the stack.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0024] Figure 1 is a perspective view of an example ultrasonic welder used in welding a workpiece.

[0025] Figure 2 is a cross-sectional view through the ultrasonic welder shown in Figure 1. DETAILED DESCRIPTION

[0026] An ultrasonic welder 10 is shown in Figure 1. A workpiece 12 typically comprising multiple components arranged on a support structure or fixture 14. The workpiece 12 has two or more components, which may be constructed of any suitable weldable material, such as plastic. Other materials may be welded as well.

[0027] The ultrasonic welder 10 includes a converter 18 to which a horn 16 is mounted. In the example shown in Figure 2, the horn 16 includes a neck 16b extending from a base 16a to a terminal end that provides a working surface 16c configured to engage the workpiece 12. A fillet provides a smooth transition between the base 16a and neck 16b.

[0028] Returning to Figure 1, the workpiece 12 is clamped between the support structure 14 by applying a force with the horn 16. A controller 20, which is connected to the ultrasonic welder 10 by an electrical connector 19, provides an electrical signal that excites the horn 16 at a desired high frequency and for a desired duration. The vibration generates heat at the interface between the components, melting the components to one another.

[0029] According to one disclosed embodiment, an air source 22 is fluidly connected to the converter 18 at an inlet 25. The air source 22 may be shop air, but other cooling fluids may be used.

[0030] Referring to Figure 2, the converter 18 includes a housing 24 having a mounting block 28 and a cylindrical structure 29 that provides a cavity 27. A piezoelectric assembly 26, which may be a stack of ceramic piezoelectric elements 26a-26e, is arranged within the cavity 27. Any suitable number of piezoelectric al elements may be used, depending upon the particular application. Wires from the electrical connector 19 transmit the electrical signal from the controller 20 to the piezoelectric assembly 26.

[0031] The mounting block 28 is provided at one end of the housing 24, and the piezoelectric assembly 26 is secured to the mounting block 28 by a fastener, such as clamping bolt 30. A pressure plate 31 is provided on the stack, which transfers the load from the fastener 30 to the mounting block 28. A hole extends through the piezoelectric assembly 26 and the pressure plate 31; the hole receives the fastener 30.

[0032] An aperture 36b is provided at one end of the mounting block 28. A fastening element such as a threaded stud 32 is received in the aperture 36b, and the base 16a of the horn 16 is secured to the stud 32 at its mounting surface. [0033] Air from the air source 22 is carried from the converter 18 to the horn 16 near its tip using an internal cooling passage provided by a first cooling passage portion (36a, 36b, collectively "36") in the converter 18 and a second cooling passage portion (38a, 38b, collectively "38") in the horn 16. To this end, the clamping bolt 30 includes a bore 36a extending therethrough from the cavity 27 to the aperture 36b to provide the first cooling passage portion 36. A hole 38a is provided in the stud 32 to provide a segment of the second cooling passage portion 38, which is in fluid communication with the first cooling passage portion 36. A passage 38b extends through the horn 16 to communicate fluid provided by the hole 38a to multiple radially extending channels 42, which terminate in exits 44 at an outer periphery of the horn's end. The exits 44 are provided axially inwardly from the working surface 16c of the horn 16, which engages the workpiece 12. In this manner, the cooling fluid does not cool the workpiece directly, which would be counterproductive to generating heat sufficient weld the workpiece components to one another.

[0034] The base 16a may include notches 40 that receive a tool used to tighten and loosen the horn 16 relative to the mounting block 28. These notches 40 are shallow such that they do not intersect the second cooling passage portion 38. Thus, the base 16a is free from any cooling holes exiting its exterior surface.

[0035] The cooling passages used to cool the horn 16 are arranged entirely internally, which prevents damage to any plumbing that would otherwise be located in the work areas susceptible to damage. Moreover, the horn 16, which is designed for welding particular workpieces at particular frequencies, will not be impacted by plumbing that might be connected to the side of the horn.

[0036] It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

[0037] Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. [0038] Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.