Patent Publication Number: US-6984921-B1

Title: Apparatus and method for resonant mounting of vibration structure

Description:
BACKGROUND 
     This application relates to mounting techniques for supporting vibratory elements from a non-vibratory support platform. The application relates in particular to techniques for supporting vibration structures which vibrate at sonic or ultrasonic frequencies, such as transducers, horns, boosters, and the like. 
     Such vibration structures typically undergo axial vibrations and include a series of half-wavelength sections with each section typically having a low (axial amplitude) nodal area and two high (axial) amplitude antinodal areas. Various types of mounting arrangements for supporting such vibration structures on a rigid support structure while substantially isolating the support structure from the vibrations have heretofore been utilized. 
     One prior mounting arrangement employs elastomeric O-rings Typically, a set of annular metal rings are used to respectively clamp O-rings against opposite sides of a mounting flange disposed on the vibration structure substantially at a nodal region. The clamping rings can be rigidly attached to a substantially rigid support structure, while minimizing the vibratory energy transmitted from the vibrating structure to the rigid structure. This vibration isolation is due to the absorbing and dampening properties of the elastomeric O-rings. The clamping of an annular nodal flange on a vibratory ultrasonic device from both sides of the flange has long been practiced. 
     However, the O-rings are subjected to wear and, in some applications, the use of an elastomeric O-ring reduces the ability to repeatedly position the vibration structure, due to the compliant nature of the rings. In order to provide enhanced stiffness or rigidity to the mount, metallic nodal mounts have been utilized. One such mount is disclosed in U.S. Pat. No. 5,590,866, which utilizes a pair of cylindrical flexural tubes, respectively bearing against opposite sides of the mounting flange on the vibration structure, and clamping means for clamping the tubes axially together and tightly against the opposite sides of the mounting flange. 
     U.S. Pat. Nos. 2,632,858 and 2,866,911 disclose techniques for supporting a magnetostrictive vibratory device by means of an elongated resonant tube, one end of which is connected to the vibratory device&#39;s nodal region, as by a threaded coupling or by soldering. 
     SUMMARY 
     This application discloses improved techniques for supporting vibration structures on rigid supports which avoid the disadvantages of prior techniques while affording additional structural and operating advantages. 
     An aspect of the techniques disclosed is that they are characterized by economy and simplicity of construction and ease of application. 
     Another aspect is the provision of a mounting apparatus which is tuned to be resonant at the resonant frequency of the vibration structure being mounted. 
     Still another aspect is the provision of a mounting apparatus which need not be coupled to the vibration structure at a nodal region. 
     Certain ones of these and other aspects may be attained by providing apparatus for mounting an elongated vibration structure which has a longitudinal axis and which undergoes axial vibrations and has a natural resonant frequency, the structure having a flange with an arcuate bearing surface disposed at a predetermined radius from the axis and with a radial end surface at an end of the bearing surface, the apparatus comprising: a mounting ring having a flexural portion defining an arcuate mounting surface terminating at a free distal end and adapted to be secured to the bearing surface of an associated vibration structure flange in coaxial bearing engagement therewith so as to inhibit relative movement therebetween, the flexural portion having a radial stop surface spaced from the free distal end and disposed for contact with the end surface of the vibration structure flange, the mounting ring having attachment structure adapted for attachment to an associated support, the flexural portion being shaped and dimensioned to be resonant at the resonant frequency and for flexing sufficient to accommodate movement of the bearing surface in response to resonance of the vibration structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
         FIG. 1  is a top plan view of a vibratory system including an embodiment of mounting apparatus mounting an ultrasonic booster; 
         FIG. 2  is an enlarged sectional view taken generally along the line  2 — 2  in  FIG. 1 ; 
         FIG. 3  is an enlarged side elevational view of the mounting ring of the mounting apparatus of  FIG. 1 ; 
         FIG. 4  is an enlarged side elevational view of the mounting apparatus of  FIG. 1 ; 
         FIG. 5  is a perspective view of the vibratory system of  FIG. 1 , illustrating assembly of the mounting apparatus to the booster; 
         FIG. 6A  is a perspective view of the mounting ring system of  FIG. 1 ; 
         FIG. 6B  is a view similar to  FIG. 6A  of a mounting ring designed for a different operating frequency; 
         FIG. 7  is a fragmentary perspective view of another vibratory system using another embodiment of mounting apparatus; 
         FIG. 8  is an enlarged longitudinal sectional view of a vibratory system of  FIG. 7 ; 
         FIG. 8A  is a further enlarged, fragmentary view of the portion designated  8 A in  FIG. 8 ; and 
         FIG. 9  is a perspective view of the mounting apparatus of  FIG. 7 , illustrating a tuning dimension. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1–5 , there is illustrated a vibratory system, generally designated by the numeral  10 , which includes a vibration structure  11  and a mounting apparatus  25  for supporting the vibration structure on an associated support (not shown). In the illustrated embodiment, the vibratory system is one designed for operation at ultrasonic frequencies and the vibration structure  11  is an ultrasonic booster. However, it will be appreciated that the vibration structure could be an ultrasonic horn or transducer or other type of device and that the vibratory system  10  could be designed for operation at other frequency ranges. 
     Referring in particular to  FIGS. 1 ,  2  and  5 , the vibration structure  11  has an elongated cylindrical body  12  having a longitudinal axis X. The mid portion of the body  12  has a relatively large-diameter outer cylindrical surface  13 , joined at its opposite ends by tapered, generally frustoconical surfaces  14 , to reduced-diameter cylindrical surfaces  15 , respectively terminating at circular end surfaces  16  and  18 . Respectively formed axially in the end surfaces  16  and  18  may be axial bores  17  and  19 , which may be internally threaded to facilitate fastening or attachment to associated devices. The body  12  is provided, intermediate its ends, with a radially outwardly projecting mounting flange  20 , which is substantially rectangular in transverse cross-section. The flange  20  has an outer cylindrical bearing surface  21  coaxial with the outer surface  13  and disposed at a predetermined radius from the axis X and terminating at annular end surfaces  22  and  23 , which are respectively disposed in planes substantially parallel to each other and perpendicular to the axis X. 
     The mounting apparatus  25  includes a mounting ring  30  and a support ring  50 . The mounting ring  30  has an annular body  31  having an annular top surface  32  substantially perpendicular to the central axis of the body  31 , the top surface  32  having an arcuate, generally concave recess  33  around its outer perimeter. The body  31  has an annular bottom surface  34  substantially parallel to the top surface  32  and provided around its outer periphery with a shallow recess which defines a stepped shoulder  35 . Formed through the body  31  substantially parallel to the central axis thereof are four equiangularly space-apart bores  36  extending between the recess  33  and the bottom surface  34 , and each provided at its upper end with a counterbore  37 . Formed in the bottom surface  34  is an annular channel  38  which extends upwardly to a level slightly above the bottom of the recess  33 , the portion of the body  31  between the upper end of the channel  38  and the top surface  32  defining a bridge  39 , which joins the main portion of the body  31  to a cantilevered flexural portion  40 . 
     The flexural portion  40  has an inner cylindrical surface  41  which defines a central bore through the body  31 , and an outer cylindrical surface  42  defined by the channel  38 . The surface  41  has a diameter slightly greater than that of the outer surface  13  of the vibration structure  11 . The lower end of the flexural portion  40  is counterbored to define a cylindrical mounting surface  43 , coaxial with the outer cylindrical surface  42 , and an annular stop surface  44 . The mounting surface  43  has a diameter substantially the same as that of the bearing surface  21  of the vibration structure flange  20 . The flexural portion  40  terminates at a distal end  45 , which may extend downwardly below the bottom surface  34 . Formed in the inner cylindrical surface  41  are a plurality of equiangularly-spaced apart recesses  46 , which may be substantially semicylindrical in shape, each recess  46  extending axially from the top surface  32  to a slight distance above the stop surface  44 , and having a radial depth extending substantially to the radial midpoint of the channel  38 , as can best be seen in  FIG. 2 . (Terms such as “top” and “bottom” or “upper” and “lower” are used herein relative to the orientation of the parts as illustrated in the drawings. However, it will be appreciated that the parts need not be disposed in that orientation in use.) 
     The support ring  50  has an annular body  51  with an annular substantially planar top surface  52  disposed substantially perpendicular to the central axis of the body  51 , and an annular bottom surface  53  substantially parallel to the top surface  52 . Extending axially through the body  51  is a center bore defining a cylindrical inner surface  54 . The top surface  52  is then counterbored to define an intermediate cylindrical surface  55  and is further counterbored to define an outer cylindrical surface  56  and an annular recessed top surface  57 . The diameter of the cylindrical surface  56  is slightly less than the outer diameter of the body  51 , cooperating with the outer surface of the body  51  to define an annular flange or rim  58  projecting slightly axially from the recessed top surface  57 . Extending through the body  51  at equiangularly spaced-apart locations are four internally threaded bores  59  substantially parallel to the central axis of the body  51 . 
     In assembly, referring to  FIG. 5 , the mounting apparatus  25  may first be assembled, with the support ring  50  being stacked upon the mounting ring  30  so that the top surface  57  of the support ring  50  engages the bottom surface  34  of the mounting ring  30 , with the flange  58  of the support ring  50  seated against the step shoulder  35  of the mounting ring  30 , as can best be seen in  FIG. 2 . The parts are arranged so that the bores  36  of the mounting ring  30  are respectively coaxially aligned with the bores  59  of the support ring  50 . The aligned bores respectively receive screws  48  which are threadedly engaged in the internally threaded bores  59  of the support ring  50  for securing the mounting ring  30  to the support ring  50 , the screw heads  49  being respectively received in the counterbores  37 . 
     The mounting apparatus  25  may then be fitted down over the upper end of the vibration structure  11  (or the vibration structure fitted upwardly into the mounting apparatus  25 ), until the stop surface  44  of the mounting ring  30  abuts the end surface  22  of the mounting flange  20 . The parts are so dimensioned that the cylindrical bearing surface  21  of the flange  20  is coaxially received within the cylindrical mounting surface  43  of the mounting ring  30  in press-fitted, coaxial bearing engagement therewith so as to inhibit relative movement therebetween. It will be appreciated that the stop surface  44  serves not only to axially position the parts, but also ensures that the mounting ring  30  is disposed coaxially with the vibration structure  11 , preventing any tilting of the parts relative to one another. The inner cylindrical surface  41  of the mounting ring  30  will then be spaced slightly from the vibration structure  11 . The cylindrical mounting surface  43  of the mounting ring  30  may have an axial extent substantially greater than that of the cylindrical bearing surface  21  of the mounting flange  20 . This also serves to facilitate assembly and minimize the chance of non-coaxial alignment of the parts. The support ring  50  may then be fixedly secured to a suitable fixed support or mount (not shown) in the known manner. 
     Alternatively, the mounting apparatus  25  may be secured to the associated support before insertion of the vibration structure  11  upwardly thereinto. Also, the mounting ring  30  may be assembled with the vibration structure  11  prior to attachment of the mounting ring  30  to the support ring  50 . 
     It will be appreciated that the relatively thin construction of the cantilevered flexural portion  40  of the mounting ring  30 , as well as its disposition substantially parallel to the longitudinal axis of the vibration structure  11 , permits a slight radial flexing of the flexural portion  40  to accommodate radial movements of the mounting flange  20 . Preferably, the mounting flange  20  is disposed at a nodal location on the vibration structure  11  for the natural resonant frequency for which the vibration structure  11  is designed, antinodal regions typically being disposed at the locations of the end surfaces  16  and  18 , all in a known manner. Because of the nodal location of the mounting flange  20 , it will undergo substantially only radial movements at resonance, which can readily be accommodated by the cantilevered flexural portion  40 , while those movements are substantially isolated from the associated rigid support. 
     It is an important aspect of the mounting apparatus  25  that the mounting ring  30  and, in particular, the cantilevered flexural portion  40  thereof, is tuned to be resonant at the natural resonant frequency of the vibratory system  10  which may, for example, be 20 khz or 40 khz. The resonance is achieved by material selection, geometry and dimensional parameters. Proper tuning may be achieved by selecting the axial length of the cantilevered flexural portion  40 , and is greatly facilitated by the semicylindrical recesses  46 . The recesses  46  are useful, not only for tuning, but also for mode refinement. In particular, these recesses allow hoop mode vibration to function near the vibration structure  11 , but allow that mode to be decoupled near the rigid annular support ring  50 . They also serve to reduce stress so that the flexural mode of vibration can function efficiently. The recesses  46  have a significant effect on the natural resonant frequency of the cantilevered flexural portion  40 , so as to function essentially as a virtual tuning tool to refine the efficiency of the mount. It has been found that, without these recesses, efficiency is greatly reduced. 
     The actual physical dimensions of the mounting ring  30  and the support ring  50  will depend upon the operating frequency of the vibratory system  10 . Referring to  FIGS. 6A and 6B , there are illustrated mounting rings  30  and  30 A, respectively designed for use in 20 kHz and 40 kHz ultrasonic systems. It can be seen that the ring  30 A is about half the size of the ring  30  and has tuning recesses  46 A which may have the same size and shape as the tuning recesses  46 , but which may be fewer in number. 
     While the mounting apparatus  25  functions extremely well, it does require that the mounting flange  20  be disposed substantially at a nodal region of the vibration structure  11  for efficient operation and effective vibration isolation. However, with certain vibration structures there is an amplitude gain from the input end to the output end which tends to shift the nodal region of the structure. Thus, in order to effectively use the mounting apparatus  25 , it might be necessary to change the position of the mounting flange  20 , thereby effectively requiring custom vibration structures. 
     Referring to  FIGS. 7–9 , there is illustrated a vibratory system  60  including a vibration structure  61  and an alternative embodiment of mounting ring  80  for mounting the vibration structure  61  on an associated support  90 . In the illustrated embodiment, the vibration structure  61  may be a probe or transducer assembly having a back slug or mass  62  and a front slug or mass  63 . The rear slug  62  and the rear end of the front slug  63  have equal relatively large-diameter cylindrical surfaces  64 . The front end of the front slug  63  has a reduced-diameter cylindrical surface  65 , joined to the surface  64  of the slug  63  by a tapered portion  66 . Two piezoceramic transducers (PZT&#39;s)  67  and  67   a  are sandwiched between the slugs  62  and  63  and have the same outer diameter as the surfaces  64 . An axial bore  68  extends through the slugs  62  and  63  and the PZT&#39;s  67  and  67   a  and may have an internally threaded portion for threaded engagement with a screw  69  to clamp together the parts of the vibration structure  61  to form a transducer having a longitudinal axis X′. 
     Integral with the rear end of the front slug  63  and projecting radially outwardly from its surface  64  is an annular mounting flange  70 , which may be substantially rectangular in transverse cross-section. The flange  70  has a substantially cylindrical outer bearing surface  71  which is substantially coaxial with the outer surface  64  and disposed at a predetermined radius from the axis X′, and terminates at annular end surfaces  72  and  73  which are substantially parallel to each other and perpendicular to the axis X′. The mounting flange  70  may be disposed substantially at a nodal region of the vibration structure  61  at the natural resonant frequency thereof, but it need not be. It will be assumed that, in the illustrated embodiment, the mounting flange  70  is disposed at a non-nodal region so that, at resonance, it will undergo vibrational deflections in a direction inclined at a predetermined non-zero acute angle to the longitudinal axis X′, so that the movement has both axial and radial components. 
     Referring in particular to  FIG. 8A , the mounting ring  80  has an outer cylindrical wall or body  81  unitary at one end thereof with a cantilevered flexural portion  82 , which includes an inclined wall  83  disposed at a predetermined angle B to the outer cylindrical wall  81 . Integral with the inclined wall  83  at the distal end thereof and projecting therefrom in a direction substantially opposite the outer cylindrical wall  81  is a cylindrical flange  84  which has a substantially cylindrical inner surface  85 , which may have a diameter slightly greater than that of the outer surfaces  64  of the vibration structure  61 . The inner surface  85  is counterbored at the forward end thereof to define a cylindrical mounting surface  86 , which has a diameter substantially the same as that of the bearing surface  71  of the vibration structure flange  70 , and an annular stop surface  87 . The flange  84  terminates at a distal end  88 , which may be spaced from the stop surface  87  an axial distance substantially equal to the axial extent of the cylindrical bearing surface  71  of the vibration structure flange  70 . The outer cylindrical wall  81  defines an outer attachment surface  89  which is substantially coaxial with the mounting surface  86 , the cylindrical wall  81  terminating at an annular distal end surface  89   a.    
     The support  90  may be generally cup-shaped, having a circular end wall  91  integral around the periphery thereof with an elongated cylindrical wall  92 . The inner surface of the cylindrical wall  92  is counterbored at its distal end to define an annular stop surface  93  and a cylindrical bearing surface  94 , which has a diameter substantially the same as that of the attachment surface  89  of the mounting ring  80 . 
     In assembly, the mounting ring  80  is assembled to the vibration structure  61  by inserting the front slug  63  through the ring  80  until the end surface  73  of the flange  70  abuts the stop surface  87  on the mounting ring flange  84 , the parts being so dimensioned that the flange bearing surface  71  is disposable in press-fitted coaxial bearing engagement with the mounting surface  86  of the mounting ring  80  to inhibit relative movement therebetween, as can best be seen in  FIG. 8 . Again, the stop surface  87  on the ring  80  serves to axially position the parts and prevent tilting of vibration structure  61  relative to the ring  80  so that they remain substantially coaxial. 
     Next, the mounting ring  80  may be assembled to the support  90  by press-fitting the attachment surface  89  inside the cylindrical bearing surface  94  of the support  90  in coaxial bearing engagement therewith until the distal end surface  89   a  of the ring  80  abuts the annular stop surface  93  of the support  90 , the stop surface  93  again ensuring that the assembled parts are coaxial. 
     The mounting ring  80  is preferably so designed that angle B is such that, when the parts are assembled in the manner illustrated in  FIG. 8 , the cantilevered flexural portion  82  and, in particular, the inclined wall  83  thereof, extends substantially in the direction indicated by the arrows A, which is substantially perpendicular to the direction of vibratory movement of the mounting flange  70  and can accommodate flexural movement in that direction. It will be appreciated that the angle B could be changed for different locations of the flange  70  relative to the nodal point of the vibration structure  61  at the resonant frequency. However, a specific angle B, such as that illustrated, has been found to work acceptably for a range of slightly different flange positions relative to the nodal point. 
     Another aspect of the vibratory system  60  is that the mounting ring  80  is designed to be resonant at the natural resonance frequency of the vibration structure  61 . This resonance may be controlled by varying the length D (see  FIGS. 8A and 9 ) of the outer cylindrical wall  81 , thereby varying the overall length of the mounting ring  80  along the outer cylindrical wall  81  and the inclined wall  83 . 
     Preferably the mounting rings  30  and  80  and the support ring  50  are formed of suitable metal materials, which afford sufficient rigidity to provide an effective mount while, at the same time, accommodating limited flexural movement. The actual material used may depend upon the resonant frequency of the system. In constructional models of the invention, the mounting ring  30  and support ring  50  have been formed of brass and the mounting ring  80  has been formed of brass or aluminum. However, it will be appreciated that other materials could be used, depending upon the operating frequencies involved. 
     While, in the illustrated embodiments, the mounting rings  30  and  80  have been assembled to the vibration structure by press-fitting, it would be possible to utilize other techniques, such as brazing, threaded coupling or the like. Also, while in the preferred arrangements, only a single mounting ring  30  or  80  is utilized to mount the vibration structure, it would be possible to use these mounting ring configurations in two-sided arrangements, utilizing two such mounting rings respectively applied to opposite sides of the mounting flange of the vibration structure. 
     While, in the illustrated embodiments, the mounting rings  30  and  80  are of unitary, one-piece construction, it will be appreciated that they could be formed of plural pieces integrally joined together. 
     From the foregoing, it can be seen that there has been provided an improved mounting arrangement for a vibration structure, which is of simple and economical construction, can be utilized without special tools or assembly equipment, is highly efficient and tunable to resonance at the resonant frequency of the vibration structure, and is usable with a variety of different types of vibration structures. 
     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims, when viewed in their proper perspective based on the prior art.