Ultrasonic vibratory devices are used for a variety of applications including, for example, tube drawing, soldering, welding, drilling, machining, and mixing. Ultrasonic vibratory devices typically include a source of vibratory energy (e.g., a transducer creating mechanical oscillation) and a coupler. The coupler conducts the vibratory energy from the transducer to a desired area or to a work piece attached to the coupler. Ultrasonic vibratory devices are generally supported in mounts from a work table or other support surface.
An important material property affecting the vibratory characteristics of ultrasonic vibratory devices is the speed of sound, which relates to the speed at which an energy wave passes through a bar of material. The speed of sound in a material is equal to <c=√{square root over (E/ρ)}, where E is Young's modulus and p is the density of the material. The speed of sound will generally vary to some extent for any given material because of variations in material chemistry, heat treatment, or amount of cold work.
During the operation of an ultrasonic vibratory device, a standing wave pattern will be established. The particular pattern depends on the operating frequency for the device and on the sound properties of the materials used. The wave pattern in the operating device defines node locations, which are those locations at which vibratory motion is at a minimum. Placement of the support for the device at the node locations desirably limits energy losses associated by absorption of the energy by the support.
U.S. Pat. No. 2,891,179 (Elmore) describes a support system for an ultrasonic vibratory device. The Elmore device includes a coupler having a length that is equal to a multiple of one-half wavelengths according to the sound properties of the material and the operating frequency of the device. The coupler includes a tapered horn at its working end. The taper of the Elmore horn is not linear and, instead, is curved as an exponential function of length. While other geometric shapes can be used, the exponential geometry does not introduce a reactive component into the impedance of the system and hence is preferred.
The Elmore device includes a support for the coupler that renders the associated vibratory device substantially force-insensitive regardless of the location on the device to which the support is secured. In other words, the vibratory device may be applied to a work area under a load without a significant shift in frequency for the device. The support structure for the Elmore device has become known in the art as an “Elmore mount” or more simply as an “E-mount”.
The Elmore mount has a length that is equivalent to one-half wavelength. For devices having very long transducer-coupler arrays, the length may be a multiple of one-half wavelengths. Referring to U.S. Pat. No. 2,891,179, the Elmore mount (FIG. 1) includes axially-extending resonant members (inner rods 36a, 36b, outer rods 44a, 44b) and connecting flanges (40a, 40b) joined to the resonant members. The connecting flanges are joined to the resonant members at a length from the free end of each resonant member that is equivalent to one-quarter wavelength of operating frequency (or an odd multiple of one-quarter wavelengths).
In later variations, the Elmore mount included a mounting sleeve extending longitudinally along the coupler of the ultrasonic device with a nodal flange included on the sleeve adapted for attachment to a support member, such as a support collar for example.
Ultrasonic devices designed to vibrate in a longitudinal mode that are not perfectly matched to an applied load experience an associated radial motion and amplitude due to Poisson's ratio. For the relatively low power applications for which the Elmore device was initially intended (e.g., welding units having maximum power of 50 watts), the associated radial effects could be neglected. However, the associated radial motion and amplitude due to Poisson's ratio creates support problems in higher power applications (e.g. metal tube drawing applications having 1000 watt power requirements).