U.S. patent number 3,930,173 [Application Number 05/412,767] was granted by the patent office on 1975-12-30 for ultrasonic transducers.
This patent grant is currently assigned to Surgical Design Corporation. Invention is credited to Anton Banko.
United States Patent |
3,930,173 |
Banko |
December 30, 1975 |
Ultrasonic transducers
Abstract
Ultrasonic transducers which are constructed to have an outer
shell surrounding a portion of the acoustic transformer of the
transducer to serve as a vibration damper and also as part of the
transducer structure. The shell is attached at a region near the
node of the transformer to control the quantity of energy
transmitted thereto. In many of the embodiments, the outer shell is
attached without the necessity of a resilient support. The
transducer is also constituted to accept a housing and form a
sealing relationship therewith to fluid, in some embodiments a
portion of the sealing means being located on the outer shell, and
in other embodiments on another portion of the transformer.
Inventors: |
Banko; Anton (Brooklyn,
NY) |
Assignee: |
Surgical Design Corporation
(Long Island City, NY)
|
Family
ID: |
26850487 |
Appl.
No.: |
05/412,767 |
Filed: |
November 5, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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153380 |
Jun 15, 1971 |
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Current U.S.
Class: |
310/26; 433/86;
433/119 |
Current CPC
Class: |
B06B
1/08 (20130101) |
Current International
Class: |
B06B
1/08 (20060101); B06B 1/02 (20060101); H01L
041/00 () |
Field of
Search: |
;310/26,8.1 ;32/58,DIG.4
;51/59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Duggan; Donovan F.
Attorney, Agent or Firm: Darby & Darby
Parent Case Text
RELATED APPLICATION:
This application is a continuation of my prior copending
application Ser. No. 153,380, filed June 15, 1971.
Claims
What is claimed is:
1. An ultrasonic energy transducer for producing vibrational wave
energy at a substantially predetermined frequency comprising:
a. magnetostrictive means for converting electrical energy into
vibrational energy,
b. a vibrating structure for producing motion including;
an acoustic impedance transformer of metallic material which is
substantially one half wavelength long at said predetermined
frequency directly connected at one end thereof to one end of said
magnetostrictive means, said transformer including a working tool
at the other end for producing motion,
an outer shell of metallic material of a length substantially one
quarter wavelength at said predetermined frequency which is spaced
from and surrounds a portion of said transformer,
and means directly connecting said shell to said transformer in
metal to metal contact so that energy can be transferred from the
transformer to said shell, said shell thereby forming a part of the
vibrating structure and affecting the characteristics of the
vibrational energy of said structure.
2. A transducer as in claim 1 wherein said outer shell includes a
first wall section of relatively heavy mass to dampen the energy
present in said shell.
3. A transducer as in claim 2 wherein the means for attaching the
shell to the transformer comprises a further wall section of
reduced thickness as compared to said first wall section located
between the transformer and the first wall section to reduce the
quantity of vibrational energy transmitted to said first wall
section from said transformer.
4. A transducer as in claim 1 further comprising a flange member
and first fastening means formed on said outer shell, housing means
surrounding a portion of said magnetostrictive means and having
second fastening means formed on a portion thereof, said first and
second fastening means mating to fasten the housing to said outer
shell with the end portion of said housing directly engaging
against the flange member of said outer shell.
5. A transducer as in claim 4 wherein said housing means forms a
chamber surrounding at least a portion of said magnetostrictive
means, means for supplying fluid to said chamber, the end portion
of the housing and the flange forming a fluid-tight seal.
6. A transducer as in claim 5 wherein said first and second
fastening means comprise screw threads.
7. A transducer as in claim 51 wherein the transformer portion
between the magnetostrictive means and said outer shell has a
flange and a first fastening means formed thereon, housing means
surrounding a portion of said magnetostrictive means and having
second fastening means formed on a portion thereof, said first and
second fastening means mating to fasten the housing to said outer
shell with the end portion of said housing against the flange
member of said outer shell.
8. A transducer as in claim 7 wherein said housing means forms a
chamber surrounding at least a portion of said magnetostrictive
means, means for supplying fluid to said chamber, the end portion
of the housing and the flange forming a fluid-tight seal.
9. A transducer as in claim 8 wherein said first and second
fastening means comprise screw threads.
10. A transducer as in claim 1 wherein the working tool is located
at the end of said transformer remote from said magnetostrictive
means, a fluid flow passage formed through said transformer having
a first opening adjacent the tool and a second opening, a housing
forming a fluid containing chamber surrounding at least a portion
of said magnetostrictive means, said chamber being in communication
with said second opening of said passage, and means for supplying
fluid to the chamber of said housing.
11. A transducer as in claim 10 further comprising current carrying
means located on the outside of said housing and outside of said
chamber and in proximity to said magnetostrictive means.
12. A transducer as in claim 2 wherein said means for attaching
said outer shell to said transformer comprises an elastic member of
metallic material between said transformer and said first wall
section.
13. A transducer as in claim 2 wherein said first wall section of
relatively heavy mass is attached to said transformer by an elastic
member of metallic material having a first portion and a second
portion which are spaced apart and concentric and are connected
together between the first wall section and the transformer.
14. A transducer as in claim 13 further comprising a housing
defining a fluid chamber for surrounding at least a portion of said
magnetostrictive means, resilient non-metallic means located on
said elastic member, said housing having an end portion fitting
over said resilient means to provide a fluid seal for the fluid in
the housing chamber.
15. A transducer as in claim 14 wherein said resilient means is
located at the junction of said first and second portions of said
elastic member.
16. A transducer as in claim 13 further comprising a housing
defining a fluid chamber for surrounding at least a portion of said
magnetostrictive means, resilient non-metallic means on said
housing member, said resilient means fitting over said elastic
member to provide a fluid seal for the fluid in the housing
chamber.
17. A transducer as in claim 1 wherein said outer shell is tubular
and has a longitudinal axis which is concentric with the
longitudinal axis of the portion of the transformer which it
surrounds.
18. A transducer as in claim 2 wherein said first wall section of
heavier mass is tubular and has a longitudinal axis which is
concentric with the longitudinal axis of the portion of the
transformer which it surrounds.
19. A transducer as in claim 2 wherein the portion of the
transducer which is surrounded by said first wall section of
relatively heavier mass is tapered, the interior of said first wall
section being generally cylindrical.
20. A transducer as in claim 2 wherein the internal portion of the
transducer which is surrounded by said first wall section of
relatively heavier mass is tapered, the interior of said first wall
section also being tapered to be generally concentric with said
internal portion.
21. An ultrasonic transducer as set forth in claim 1 wherein said
transformer working tool has a tip portion whose center of mass
lies off-center of the longitudinal axis of the transformer.
22. An ultrasonic energy transducer for producing vibrational wave
energy at a substantially predetermined frequency comprising,
magnetostrictive means for converting electrical energy into
vibrational energy, an acoustic impedance transformer of metallic
material attached to one end of said magnetostrictive means, said
transformer including a first portion adjacent said
magnetostrictive means, a workpiece, and a second portion joining
said workpiece and said first portion, said transformer
transferring the vibrational energy of said magnetostrictive means
to said workpiece, an outer shell of metallic material having a
length equal substantially to an odd multiple of a quarter
wavelength of the predetermined frequency surrounding at least a
part of said second portion of said transformer, and means of
metallic material for attaching said shell to said transformer at a
position substantially in the region of the node of said first and
second transformer portions to transfer vibrational energy to said
shell so that said shell becomes a part of the transducer to affect
a characteristic of the vibrational energy at the workpiece.
23. A transducer as in claim 21 wherein said outer shell extends
only in a direction toward the workpiece end of said
transformer.
24. A transducer as in claim 21 wherein said outer shell has a
first section which extends in a first direction toward the
workpiece end of the transformer and a second section which extends
in the opposite direction toward the magnetostrictive means.
25. A transducer as in claim 21 wherein said outer shell has a
first wall section of relatively heavy mass which serves as an
energy damper which surrounds at least a part of said second
portion of said transformer.
26. A transducer as in claim 25 wherein a second wall section of
lighter mass than said first wall section is located between said
first wall portion and the point of attachment of the outer shell
to the remainder of the transformer to reduce the amount of energy
transmitted to said first wall portion.
27. A transducer as in claim 25 wherein the outer surface of said
first wall section is formed with a depression.
28. A transducer as in claim 26 wherein the outer surface of said
first wall section is formed with a depression.
29. A transducer as in claim 25 wherein the free end of said first
wall section is of reduced thickness as compared to remainder of
said first wall section.
30. A transducer as in claim 26 wherein the free end of said first
wall section is of reduced thickness as compared to remainder of
said first wall section.
31. A transducer as in claim 22 further comprising a flange formed
on said transformer substantially in the region of said node, and
means for attaching said outer shell means to said flange.
32. A transducer as in claim 22 further comprising a flange formed
on said transformer substantially in the region of said node,
housing means, and means for attaching said housing to said
transducer with one end thereof directly engaging said flange.
33. A transducer as in claim 32 wherein said attaching means
comprises mating threads on said transformer and said housing.
34. A transducer as in claim 31 wherein said attaching means
comprises means for making an engaging fit with said flange.
35. A transducer as in claim 31 wherein said attaching means
comprises threaded means.
36. A transducer as in claim 30 wherein said outer shell comprises
a first portion which extends in a first direction toward the
workpiece end of the transformer and a second portion which extends
in the opposite direction toward the magnetostrictive means, said
attaching means including means for holding said first and second
portions together and to said flange.
37. A transducer as in claim 36 wherein said last-named means
includes a resilient support of nonmetallic material between said
transformer and said first and second portions.
38. A transducer as in claim 36 wherein said last-named means
further includes threaded means for holding said first and second
portions together.
39. A transducer as in claim 37 wherein said last-named means
further includes threaded means for holding said first and second
portions together.
40. A transducer as in claim 22 wherein said outer shell is
substantially one quarter wavelength long at said predetermined
frequency of vibrational energy.
41. An ultrasonic transducer comprising magnetostrictive means of
metallic material for converting electrical energy into vibrational
energy of a predetermined frequency including a component which
travels longitudinally of the magnetostrictive means, an acoustic
impedance transformer of metallic material having one end attached
to one end of said magnetostrictive means and a free end for
performing work, said transformer means including a portion which
in conjunction with other portions of the transformer produces a
component of vibrational energy at the tip of said free end which
moves substantially transverse to the longitudinal axis of the
transducer, and an outer shell of metallic material substantially
an odd number of quarter wavelengths long at said predetermined
frequency connected to said transformer spaced from and surrounding
a portion of said transformer in metallic material to metallic
material contact in the vicinity of a node point of the vibrational
energy produced therein for receiving the vibrational energy and
controlling at least one characteristic of the vibrational energy
produced at the tip of said free end of said transformer.
42. A transducer as in claim 41 wherein said outer shell is
substantially one quarter wavelength long at said predetermined
frequency of vibrational energy.
43. An ultrasonic transformer as in claim 41 wherein said portion
of said transformer for producing the component of thd vibrational
wave energy which moves substantially transverse to the
longitudinal axis of the transducer, includes a mass lying off
center of the longitudinal axis of the transformer.
44. An ultrasonic transducer comprising magnetostrictive means for
converting electrical energy into vibrational energy having a
component which travels longitudinally of the axis of the
magnetostrictive means and the transducer, an acoustic impedance
transformer having a first portion attached to one end of said
magnetostrictive means and a second portion with one end attached
to said first portion of said transformer and having a tool tip
with mass which lies off-center of the longitudinal axis of the
transformer and a free end, said transformer producing motion at
the free end of the toop tip having components both along and
substantially transverse to the longitudinal axis of the
transducer, and means for supplying fluid to the moving tool tip,
said last-named means including at least a portion of the acoustic
impedance transformer having a fluid supply passage formed
therethrough, said passage opening into the inner face of the tool
tip and including a depression on the inner face in which the fluid
is adapted to flow.
45. A transducer as in claim 44 wherein said tool tip is
curved.
46. A transducer as in claim 44 wherein said tool tip includes a
curved portion and the depression on the inner face of said tool
tip extends for at least a part of said curved portion.
47. A transducer as in claim 46 wherein said tool tip terminates in
an end tapering to a point, the depression on the inner face of the
tool tip terminating short of the free end of the tool tip.
48. A handpiece for producing vibrational energy comprising,
means for converting electrical energy into vibrational energy,
impedance transformer means having one end attached to said
converting means and a second free end having a workpiece,
a flange member attached to and radially extending from said
acoustic impedance transformer means,
tubular housing means surrounding at least said converting means
while leaving a space between the inner surface of said housing
means and said converting means, said housing means including means
closing one end thereof,
means for supplying fluid to the interior of said housing through
said closed end, and
mating fastening means on said housing means and said transformer
means to hold said housing means to said transformer means with the
other end of said housing means directly engaging said flange
member and forming a fluid tight seal with said flange member.
Description
Ultrasonic transducers are well known devices for converting
electrical energy into vibrational motion at ultrasonic
frequencies, broadly considered to be in the range from 1 khz to
100 khz. Many of these transducers use a stack of magnetostructive
elements for producing the desired energy conversion.
The present invention relates to improvements in ultrasonic
transducers. More specifically, the transducers of the invention
are of the magnetostructive type and include a stack of elements of
magnetostructive material, a workpiece or tool, and an acoustic
transformer between the stack and the workpiece for transmitting
energy from the stack to the workpiece. The transformers are of a
type which include an outer shell which is attached near or at a
node point of an internal part of the transformer. The shell serves
as a support by which the transducer can be held and/or a housing
attached. The shell forms a part of the resonating structure and
its characteristics can be changed to alter the resonant frequency
of the transducer. It is preferred that the outer shell have a
portion of relatively heavy mass which will serve as a vibration
damper.
In the preferred embodiments of the invention, the outer shell is
attached to the other part of the transformer without the use of a
resilient support. This means that the entire instrument can be
sterilized, such as by autoclaving, without any risk of damaging
it.
Also, in accordance with preferred embodiments of the invention,
the transducers are constructed in a manner such that a housing can
be provided in which a fluid can be circulated to cool the stack
members. The structures are such that the housings can be fastened
to the outer shell or another part of the transducer transformer.
In many cases, this can be done without the need of any resilient
sealing members. In some of the embodiments, a screw thread is used
as the fastening means. This prevents the insert (stack,
transformer and workpiece) from being pulled axially out of the
housing.
Also in accordance with the invention, novel transducer structures
are disclosed which can support high stress loads and which have a
large stroke of motion of the workpiece.
It is therefore an object of the invention to provide novel
ultrasonic transducer structures having an outer shell which is
used as a support member.
A further object is to provide ultrasonic transducers which are
made entirely of metal material.
Another object is to provide novel ultrasonic transducers having
arrangements for attaching a fluid containing a housing thereto
without the need of a sealing element.
Yet another object is to provide novel ultrasonic transducer
structures which are constructed with a flange member adjacent to
an outer shell, the flange serving as one sealing surface for a
fluid containing housing.
Other objects and advantages of the present invention will become
more apparent upon reference to the following specification and
annexed drawings, in which,
FIGS. 1A and 1B when taken together, show partially in
cross-section a one embodiment of a transducer in accordance with
the invention in cross-section;
FIG. 2 is a diagram showing the longitudinal motion of the
vibrational energy of the transducer of FIG. 1;
FIG. 3 is a front view of the transducer of FIG. 1;
FIG. 4 is a cross-sectional view of the transducer of FIG. 1 taken
along the lines 4--4 of FIG. 1;
FIG. 5 is a fragmentary view of a front portion of a transducer,
taken in cross-section, of another embodiment of the invention;
FIG. 6 is a cross-sectional view of the front portion of yet
another embodiment of transducer;
FIG. 7 is a diagram showing the longitudinal component of motion of
the vibrational energy of the transducer of FIG. 6;
FIG. 8 is a view in cross-section of the front portion of still
another transducer;
FIG. 9 is a view partially in cross-section of a further embodiment
of a housing for a transducer; and
FIGS. 10-14 are views partly in cross-section of portions of still
further embodiments of transducers.
FIGS. 1A, 1B and 2-4 depict one embodiment of the invention and the
general operational aspects thereof. The insert or transducer T
includes a stack of laminations 10 of a suitable magnetostrictive
material, for example, nickel or a nickel alloy. The left end of
the stack laminations are shown brazed or welded together at 11. An
acoustical impedance transformer 14 has one end connected, such as
by brazing, to the other end of the stack at 18. A workpiece or
tool 12 is connected to be part of the transformer 14. This
connection also can be made by brazing or made as part of the
central section of the transformer.
The acoustical impedance transformer 14 is shown as having a
central section formed by pieces 14a, 14b and 14c. It also includes
the tool 12 and the inner and outer shells 30a and 30b of a
resonant elastic support member 30. Each of these sections is in a
general tubular shape, except for the tool, and the cross-sectional
area of the central portions 14a, 14b and 14c decreases between the
end 18 of the stack 10 and the work tool 12. Thus, the mass of
respective sections decrease toward the tool. The central section
of the transformer including the tool 12 can be made of one solid
piece of material which has been suitably machined and bent to form
the tool shape or of separate pieces of material joined together.
The tool 12 can be of any suitable shape which will operate with
the transducer. A fluid flow passage 23 is formed through the
entire length of the central portion of transformer 14.
The main function of the acoustical impedance transformer 14 is
transporting energy from the stack of magnetostrictive material 10
to the work tool 12. The transformeer 14 is designed to have its
resonant frequency (when attached to the tool 12) substantially
equal to the resonant frequency of the stack 10 so that the
junction 18 between the two is at or close to the loop (end) of the
longitudinal component of vibration of the stack. At this point the
stress produced by the component of longitudinal vibration is lower
and the losses of energy due to the reflection of standing waves is
negligible.
The acoustical transformer 14 also serves the function of
increasing or decreasing the stroke of vibration of the tool 12 in
a desired manner when the stack is vibrating with a given stroke of
motion. For the particular transformer construction shown in FIG.
1, the distribution of the longitudinal motion of mass particles in
a given cross-section is shown directly below in FIG. 2. The end of
the stack 10 which is connected to the transformer section 14a at
point 18 imposes a longitudinal component of vibration upon the
section 14a of a magnitude corresponding to the amplitude A.sub.0.
This is a loop of the longitudinal component of motion whose
amplitude changes in a cosine function from the end 11 toward the
end 18. The amplitude of motion decreases from A.sub.0 at point 18
as it progresses toward the junction 15 of the two transformer
sections 14a and 14b. Junction 15 is substantially one-quarter
wavelength or 90.degree., at the resonant frequency of the
transformer, from the loop 18. It is, therefore, close to the nodal
point where the amplitude of longitudinal vibration is zero. From
loop point 18, the amplitude of longitudinal vibration of a
transformer section 14a at any point X is given as A.sub.x =
A.sub.0 cos x and decreases to zero at node point 15.
The maximum velocity (v.sub.max) of mass particles at the loop
point 18 is given by the following formula:
where f is the resonant frequency of the transducer. The maximum
acceleration (.PHI..sub.max) of mass particles at the same loop
point 18 is given by the following formula:
From the node point 15, toward the tool, the amplitude of the
longitudinal motion begins to increase at a faster rate in
transformer section 14b than the increase on the other side of the
node for a corresponding distance of the transformer section 14a.
The reason that the rate of increase is greater is because of the
smaller mass per unit acoustical length of the transformer section
14b than for section 14a.
Transformer 14 is a resonant vibrator having four loops of
longitudinal vibration, at points 18 and 21, 32 and 39 and two
nodes at points 15 and 36. Its acoustical length is .lambda./2 =
180.degree. = .pi. radians. Masses on each side of the nodes 15 and
36 are moving longitudinally in opposite directions. The node is a
region of substantially no longitudinal motion. Therefore, points
can be found on both sides of the node where the kinetic energies
are in substantial equilibrium.
As explained previously, the masses on each side of the nodes are
different. By suitably selecting the masses on each side of the
nodes 15 and 36, a desired magnification factor M can be obtained
for the transducer. In a simple vibrator, considering a mass and
velocity m.sub.o and v.sub.o on the left side of a node and a mass
and velocity m.sub.1 and v.sub.1 on the right side at any point
where an equilibrium holds the following will apply: ##EQU1## The
magnification factor M for this case is as follows: ##EQU2## A
greater stroke of motion is obtained at the end of the acoustical
transformer with the smallest cross-section since it has the
smallest mass. This explains the more rapid increase in the
amplitude of motion due to the longitudinal component of vibration
from node 15 to point 17, where section 14b joins section 14a, and
the still more rapid increase where the mass of transformer section
14c is even smaller from point 17 to 21. There is also a
magnification from point 21 to the free end 22 (tip) of the tool 12
since the latter has a smaller mass per unit length than the
transformer section 14c. If the tool tip 12 were substantially
straight, then in FIG. 2, A.sub.1 would represent the amplitude of
the component of longitudinal vibration at the output end point 22
of the transformer. The actual stroke length at 22 is equal to
2A.sub.1 since the end of the transformer vibrates longitudinally
in both directions for a distance A.sub.1 about the point shown. As
explained below, the curved workpiece 22 shown in FIG. 1 also
exhibits flexural motion, i.e. motion transverse to the
longitudinal axis of the insert.
Due to variances in the physical tolerances of the parts of the
insert encountered during manufacturing, as well as a changing load
which is encountered at the working end of the tool 12, the
resonant frequency of similarly designed inserts made on a
production basis and operating under different load conditions will
differ. Variations are also encountered in the acoustical length
and the position of the node point for the same reasons. This
length should be 360.degree. for the entire vibrator structure from
the end of the stack to the end of the working tip, regardless of
the actual physical length of the transducer and the influence of
the load. Both these factors combine to create a working frequency
for the transducer which can be different from the designed
resonant frequency at which maximum efficiency will be
obtained.
Since, because of manufacturing tolerances and different working
conditions, it is not possible to design a transducer structure
which will always oscillate at a particular frequency and the
position of the node point cannot be accurately predicted. Also, as
pointed out above, the node position changes with changing load.
The present invention provides a transducer having an elastic
support for the outer shell in which the support can be attached to
the central tubular section within a fairly wide region at an
around the node point. The elastic support controls the flow of
energy. Its mass becomes, to some extent, an integral part of the
vibrating structure. If the support is attached at the output side
of the node, it can serve as a dampener of vibrations at the output
end of the support. If it is attached at the input side to the node
it can serve as an amplifier. If it is attached directly at the
node it will not adversely affect the operations of the transducer.
It should be understood, however, that the mass of the support
makes it an energy accumulator and the vibrating energy will be
converted into heat. In the embodiment shown in FIG. 1, the
majority of the heat is produced on the inner shell section 30a of
the support. Some of this is transported to the outer shell section
30b and to the surrounding medium, such as water, if used.
The support is constructed in such a manner that it permits the
transducer to be held by the outer shell portion 30b with little
vibration being transmitted thereto. The amount of ultrasonic
vibratory energy transmitted to the outer support shell 30b depends
on many factors, one of which is the ability of the shell to absorb
or transmit the energy. In the embodiment of FIG. 1, the front
portion 38 of the outer shell section 30b is designed to function
as an energy damper by being of a relatively large mass. The large
mass section 38 dissipates a large portion of the energy which
passes through the nodal region of outer section 30b. It also has a
low amplitude of motion and transmits some of the vibrational
energy to the surrounding medium, air or fluid, in which the
transducer is used. The resonant support 30 is part of the entire
vibrating structure and it effects the performance and behavior of
the transducer as a whole.
The resonant support 30, and particularly the outer section 30b,
provides a means by which a cover or housing can be fastened to the
transducer. Further, it shields the central section 14a, 14b, 14c
of the internal section which is capable of radiating high energy
loads. This is also desirable.
In several of the embodiments of the invention to be described, an
outer shell is provided with a type of fastening means which can
form a water tight seal without the use of an O-ring or other
similar sealing member. This greatly simplifies the transducer
construction where it is to be used with a cooling fluid. Further,
as previously described, by suitably shaping the outer shell or
modifying the mass of one or more of its sections, the transducer
can be "tuned", within limits, to a desired resonant frequency and
output stroke of motion after it has been manufactured.
As seen in FIG. 1, an elastic support 30a is used to attach the
outer shell 30b to the transducer. Elastic support 30a is attached
at its end 31 to the central section of the transformer at node
point 15 or in the region therearound. This region around the node
has a given amplitude of vibration on each side of the actual node.
The amplitude of this vibration can be small and will be
substantially zero at the node. This small, or zero, amplitude
vibration is transmitted to the outer shell 30. The elastic support
30a is relatively thin to reduce the transmission of energy to the
outer shell 30b.
The outer shell is attached to the end 32 of the elastic support
30a which is remote from the end 31. Section 30b extends over and
is coaxial with the elastic support 30a and projects toward the
nodal region of the outer shell.
The first portion of outer shell 30b which is attached to the
elastic support 30a, has a relatively small wall thickness as has
the elastic support 30a for restricted transmission of ultrasonic
energy toward the nodal region of the outer shell 30b.
In the proximity of its nodal region, the wall of the outer shell
is formed with a screw thread 35 and a flange 36 which is to be
used for attaching a housing 40. Beyond the flange there is a
thinned down wall portion 37 which also serves to reduce the
quantity of energy transmitted through the support. The portion 38
of heavier mass than any other portion of sections 30a or 30b,
terminates the shell at its free end 39. Portion 38 serves as a
vibration damper as previously explained.
While point of attachment 31 is a loop for the elastic support 30a,
the amplitude of the longitudinal component of vibration is reduced
going to the left toward the junction 32 of sections 30a and 30b.
Since elastic support section 30a and the thin walled portion of
section 30b which is substantially coaxial with elastic support 30a
have substantially a .lambda./4 acoustical length and relatively
thin cross-section, they present a high resistance to the
transmission of ultrasonic energy.
The elastic support section 30a together with the shell, including
piece 38 of heavy mass, are acoustical sections which together are
close to .lambda./2 long. Whatever motion is imposed on the outer
shell at point 32, its amplitude decreases toward the node point
where the flange 36 islocated. Finally, because of the large mass
of the portion 38 beyond the flange, there is relatively little
vibration of the shell to the right of the nodal point because, as
previously described, this greater mass moves with a lower
stroke.
The transducer structure is well suited for accepting and retaining
the tubular housing 40 through which there is fluid-flow
communication in a chamber 66. As seen in FIG. 1, a through passage
23 is formed throughout the entire length of the transformer 14.
This passage opens at the end 21 of section 14c so that fluid will
be directed by a groove onto the inner surface of the tool 12.
Another passage 24 is formed through the wall of the transformer so
that there will be fluid communication between the housing chamber
66 and the passage 23.
The inner end of housing 40 is threaded at end 42 to mate with the
thread 35 on the support 30. The inner surface of flange 36 tapers
inwardly to mate with an outward taper on the end 43 of the
housing. When fastened tightly, the end 43 of the housing butts
against the wall of the flange 36 to form a fluid-tight seal
against the fluid in the housing. The two opposite tapers on the
flange and housing prevent flowing of the housing material.
The housing 40 can be made of plastic or any other similar suitable
electrically non-conductive material. The portion of the housing
immediately to the left of the threads 42 can be shaped as desired
to provide a suitable grip for the fingers of the operator using
the transducer. This gripping section can extend for any desired
length consistent with the total overall length of the transducer
and is shown as terminating the small tapered section 44. To the
left of section 44 the housing is formed with a widened section 46.
A groove 48 is cut in section 46 to accept and hold an O-ring 50 to
prevent penetration of moisture to the energizing coil 58. The wall
thickness of the housing is then reduced to provide an area between
a pair of upstanding ring bosses 54, 56 on which is wound the coil
58. The coil 58 is in close proximity to the stack elements 10 to
supply the necessary energizing force to the stack so that it will
exhibit a magnetostrictive effect. A circuit for supplying the
current is disclosed in the copending application of Gabriel
Popescu entitled "Generator For Producing Ultrasonic Energy," Ser.
No. 152,947 filed June 14, 1971, which is assigned to the assignee
of the subject invention.
The housing 40 terminates in a threaded section 59 (FIG. 1B) which
has a groove 60 which accepts and holds another O-ring 62 which
holds the leads supplying current to the coil 58 in place. End
section 59 has a passage 64 formed through it which communicates
with the chamber 66 of housing 40.
A cover 70, which also can be of plastic or any other suitable
material, fits over the end of housing 40 and that portion on which
the coil 58 is located. A tight engaging fit is made between the
inner surface of the cover 70 and the O-rings 50 on one end and the
thread and O-ring 62 on the other so that the cover will not slide
or unscrew off. The end of the cover 70 has an internal thread 74.
An end cap 76, which is also of an insulating material, is pressed
against the housing 40 when the cover is screwed on. A pair of
leads 69 for supplying current to the coil 58 pass through end cap
76 as well as a conduit 80 for supplying water or other similar
cooling fluid to the housing chamber 66. The end of the conduit 80
fits into the passage 64 at the end of the housing 40. The portions
of the leads 69 and conduit 80 outside of housing 40 are normally
contained within a common sleeve (not shown) or other suitable
member.
The cooling fluid coming in conduit 80 into the chamber 66
completely surrounds the stack 10 and its laminations. This fluid
passes from chamber 66 into the opening 24 in the transformer (FIG.
1A) and through the passage 23 to exit onto the tool 12. It should
be noted that the fluid in chamber 66 never comes into contact with
the current carrying coil 58. This is a decided advantage from the
point of view of safety since the possibility of any short circuits
occurring between the electrical current and the water.
As should also be noted, the housing 40 is attached to the
transducer in the area (35 and 36) of the node of the outer shell
30b. This reduces or substantially eliminates the vibration which
is transmitted to the housing 40. This is also advantageous since
it makes it easier for the operator to use the transducer.
The transducer of FIGS. 1-4 has several advantages. It is simple in
construction while still being efficient in the transmission and
utilization of energy. No complicated tubes or other arrangements
are necessary for directing fluid onto the tool. Further, no
resilient support members are used, such as O-rings, as in the case
with other prior art transducers. In addition, the threaded
engagement between the housing 40 and the transducer insert (stack,
transformer and tool) prevents separation of the two which might
more easily take place if a sliding or press-fit were used between
the two.
It should be understood that the transducer of FIG. 1 also operates
the curved tool tip 12 to have a flexural component of motion at
its end 22. This is in addition to the longitudinal component of
the vibrational energy which was discussed previously. In the case
of the curved tip, the amplitude of the longitudinal vibration
component decreases from point 21 substantially to zero at the tip
end 22 rather than increases as in the case of a straight tip. The
curved tip 12 of FIG. 1A has a maximum amplitude of flexural
vibration at its end 22 as it moves back and forth transverse to
the insert longitudinal axis on each side thereof. The flexural
component also has a mode point located at the mode point 15
previously described for the longitudinal component. This node
point for the flexural vibration is, however, more than one
wavelength away as measured in terms of the standing wave of the
flexural component of motion. The flexural component is produced
due to the curved portion of the tool tip which lies off center of
the longitudinal axis of the other portions of the transformer,
that is, the tip provides an asymmetric mass to the compressional
waves in the structure which produce the longitudinal motion. When
a curved tip is used, the structure acts to convert compressional
energy, normally producing longitudinal motion, to flexural motion
at the tool tip 22.
FIG. 5 shows another embodiment of transducer which is similar to
that shown in FIG. 1. The main difference here being that the
portion of the internal section of the acoustical transformer
between the node point 15 at which the connection of the elastic
support 30a is made, and the end 21 of the internal section of the
transformer is formed by a conical tapering section 69 instead of
using the two tubular sections 14a and 14c as in FIG. 1. This
arrangement operates satisfactorily. However, the magnification
factor obtained by the use of a transformer with a conical section
is not as great as with all cylindrical sections. As in the case of
FIG. 1, the construction of housing 40 can be the same.
FIG. 6 shows another embodiment of the invention which in many
respects is similar to that of FIG. 1. Here, the support 130 is
made slightly different in that the portion 132 which joins the
elastic support 130a and the outer shell section 130b is relatively
thick. This thickened portion 132 is also formed with a groove 139
in which is located a resilient O-ring 141. Outer section 130b is
also formed with a thickened annular rib 135 which serves as both a
damper for the resonant support and a stop for the end of a housing
140. The end section 138 is tubular and of relatively large mass to
also serve as a damper. The housing 140 is somewhat different from
that of FIG. 1 in that it is held to the insert by a press-fit over
the O-ring 141. The O-ring provides the seal for the fluid in
chamber 66.
With the foregoing exceptions, the construction of the transducer
of FIG. 6 is similar to that of FIG. 1. It should again be noted
that the outer shell is connected to the central portion of the
transducer in a manner to reduce the vibrations present on the
outer shell. Also, no resilient mountings are needed.
FIG. 7 shows the pattern of the longitudinal component of the
vibrational motion for the stack and central region of the
transducer. The operation of this transducer is similar to that of
FIG. 1. That is, if the tool tip is substantially straight the
amplitude of the longitudinal motion increases between the start of
the tip and its end 22. If the tool tip is curved, the amplitude of
the longitudinal motion decreases and, instead, the amplitude of
the flexural component of motion increased to maximum at the end of
the tip.
FIG. 8 shows another embodiment of the invention which is similar
to that of FIG. 6. Here, however, the O-ring for holding the
housing is located on the housing itself instead of on the
resonator support. A groove 151 is formed on the inner wall
adjacent the end of the housing 150 and an O-ring 152 is located
therein. This provides a seal for the fluid within the chamber 66
of the housing. The elastic support 130a and portion of the outer
shell 130b have substantially the same wall thickness and the
thickened section 132 of FIG. 6 is eliminated. The operation of the
transducer of FIG. 8 is similar to that of FIG. 6.
In some applications it is desired to have an increased stroke
length for the tool of the transducer. Stroke length is limited by
the strength of the material forming the acoustical transformer and
the tool itself. The stess produced by the longitudinal component
of motion is given by the following formula:
where:
f = the resonant frequency of the transducer
p = the density of the transducer material
C.sub.l = the velocity of sound For a given frequency and stroke
length, the stress in a given cross-section of a chosen shape is
directly proportional to the density of the metal used.
It has been found that titanium is a suitable metal which can
support a high stress. Titanium also has another advantage in that
it is inert. This renders it particularly useful for some
applications such as, for example, where the instrument is to be
sterilized. However, titianium has disadvantages in that it cannot
be readily brazed either to itself or to other metals as in the
case of the more common materials, such as stainless steel, which
are normally used for acoustical impedance transformers and
tools.
In accordance with the invention, various forms of transducers are
disclosed which can be made of titanium and which also are
constructed in a way such that these transducers can be
manufactured fairly easily. As in the case of the transducers
previously described, a support member is also used for the same
purposes mentioned previously.
In FIG. 10, a transducer is shown having the usual stack of
laminations 10. To the end 18 of the stack adjacent the acoustical
impedance transformer, a stud 170 is fastened, such as by welding
or other suitable technique. The stud 170, which can be of Monel,
has a threaded bolt 172 on the end thereof.
The acoustical impedance transformer 214, which is preferably made
of titanium, has a threaded blind bore 182 formed in its end of the
first internal section 214a adjacent the stack so that the
transformer can be connected to the stack by the bolt 172 and
energy transmitted to the transformer. This eliminates the need to
weld the transformer to the stack. The transformer 214 is
substantially one-half wavelength long between its input end point
173 adjacent the stack and its output end 174. The stack 10 is also
one half wavelength long so that the total length of the transducer
is one wavelength. The tool is preferably formed of the same piece
of material which forms the transformer 214 For example, after the
end of the piece of material forming the transformer is made to
size, the tool end is bent to the curved shape shown.
The node of the internal section of transformer 214 is at point
183. Between the input end 173 and the node point 183, the
transformer section 214a is of generally cylindrical shape and is
substantially one-quarter wavelength long. There is a conical taper
in the internal section 214b between the node point 183 and the
output end 174. The tapered section is substantially a quarter
wavelength long. As in the case of the transducers previously
described, points 173 and 174 are loops of the longitudinal
vibration of tool 176. The magnification factor between the output
end 18 of the stack and point 174 is determined by the mass of the
transformer sections on each side of the node point 183. Since the
mass to the right of the node point is smaller and gradually
decreases, a positive magnification factor is obtained.
As previously described, it is difficult to manufacture transducers
on a basis such that a precise resonant frequency and node can
always be obtained. Therefore, the transducer of FIG. 10 is also
provided with an outer shell support 190 for the same reasons as
previously described. The support is also made of titanium and is
attached to the transformer 215 at the node point 183. The support
190 can be made of a separate piece and attached to the transformer
by suitable techniques such as, for example, welding. The first
portion 191 of the support adjacent the transformer node 183 is
made relatively thin to reduce the amount of energy transmitted to
the remainder of the support. The outer wall of portion 191 is
threaded at 193 to accept the mating screw threads 42 of housing
40.
A flange 194 is formed on the support adjacent the threads 193. The
wall of the flange tapers inwardly to form a tight fit with the
outwardly tapering end 43a of the housing to provide a fluid tight
seal for the fluid in the housing chamber 66. From the flange 914
the flange terminates in a cylindrical section 197 of heavier mass
than the first section 191. Section 197 serves as a dampener for
the vibrations.
The support 190 forms part of the vibrating structure. It is
substantially one quarter wavelength long. Its left end is
connected to the node 183 of the central section of the transformer
and its right end is of a loop. Further, the thinned wall section
191 chokes energy transmission. Because of these factors, the
support member 190 vibrates very little. Also, the housing 40 is
attached to the support by thread 193 adjacent the node 183 so it
also receives relatively little energy.
FIG. 11 shows another form of transducer which is similar to that
of FIG. 10. The main difference is that the threads 202 which mate
with threads 42 on housing 40 are located on the first internal
section 214a of the acoustical transformer instead of on the
resonant support member, as in FIG. 10. The threads 202 are in the
general location of the node of the transformer. Therefore, there
is very little energy transmitted to the housing 40. The wall of
the heavier mass dampening portion of the resonant support 209 is
thinned out at 210, to the right of the transformer node, to reduce
the quantity of energy transmitted to the portion 209.
FIG. 12 shows still another embodiment of transducer which can be
made of titanium and which is in some respects similar to that of
FIG. 11. This is the preferred embodiment of transducer. Here, the
threads 202 to hold housing 40 are located on the outer wall of the
first internal transformer section 214a to the left of the node
point. The end 43b of the housing 40 forms a fluid-tight seal
against a flange 219 which is the beginning of the outer shell of
support 230. The connection of the support 230 to the transformer
section 214a is at or in the region of the node point of the
internal transformer section and is made by the flange 219 and a
thin wall section 232. Wall section 232 is generally perpendicular
to the flange 219 and its reduced thickness reduces the amount of
energy transmitted to the main portion 234 of the resonant
support.
The outer shell is a portion of the transducer structure and
determines its resonant frequency. The thick wall portion 234 of
the outer shell serves as a damper, as in the supports of the
embodiments previously described. However, unlike the support of
the other embodiments, the inner wall of portion 234 of the
resonant support lies generally parallel to and is concentric with
the conical outer surface of the second internal section 214b of
the transformer. Because of the heavy mass of portion 234 and also
because of its concentricity with transformer section 214b, the
vibrations are damped and also there is good shielding of any
vibrations radiated from the conical transformer section.
The front end of the support 230 is stepped down at 236 to a
generally tubular shape. The shape of the front end member 236 is
used to "tune" the resonant frequency of the transducer. The
generally concave shape of the center section 234 is also
advantageous since it provides a gripping surface for the thumb and
finger of the user of the transducer. The shape can also be useful
in tuning the transducer.
FIG. 13 shows still a further embodiment of transducer which is
also suited to be manufactured from a high stress metal, such as
titanium. Here, the first internal section 214a of the transformer
is formed with a flange 250 at the node point. A resilient O-ring
252 is backed up against the flange. The outer shell support 260 is
in this case formed by front and rear pieces 261 and 262. Front
piece 261 has a tubular front section of heavy mass adjacent the
tool which is used as a damper. The rear portion of piece 261 is
formed eith a flange 264 having screw threads 265 on a reduced
diameter shoulder 266 behind the flange.
The rear piece 262 extends toward the rear of the transducer. A
generally L-shaped ring flange 267 is formed on the front end of
piece 262. Screw threads 268 are formed on the front end of flange
267 to mate with the threads 265 of the first outer shell piece
261.
These two pieces 261 and 262 are fastened together to form the
complete support structure. The shoulder 266 of front piece 261
engages the transformer flange 250. The shoulder of the ring flange
267 of the rear piece 262 engages the O-ring 252 which in turn
engages the transformer flange 250. The two pieces are tightened
together by the mating threads 265 and 268.
The point of joining the two pieces of the support is at the flange
250, which is a node. The front piece 261 serves as a damper. As
should be apparent, the outer shell support 260 is held to the
transformer by the resilient O-ring 252. This is the only
embodiment of the invention where such an arrangement is used. The
rear piece 262 of the support serves as a damper and for the
purpose of dissipating heat. Screw threads 271 are formed on the
outer surface of the piece 262 in order to accept and hold the end
of the housing 40. The fluid-tight seal to chamber 66 is made by
the O-ring 252.
FIG. 14 shows still a further embodiment of the invention which is
in some respects similar to that of FIG. 13. Here, the O-ring 252
is eliminated and the threaded portions 265 and 268 of the
respective pieces 261 and 162 are sized so that shoulders of the
two pieces will engage the flange member 250, located at the node
point of the internal section of the transformer. This is
essentially a press-type fit for the resonator structure.
In each of the embodiments of FIGS. 1-8 and 10-14, a fluid-flow
passage 23 is shown extending the entire length of the transformer
so that fluid can be directed onto the tool. An opening 24 is also
shown in the transformer to provide communication between the fluid
in the housing chamber 66 and passage 23. It should be understood
that in some cases, the transducers can be used without a fluid. In
other cases, a fluid can be used only for the purpose of cooling
the stack of laminations.
FIG. 9 shows a housing arrangement for the latter purpose. This
housing can be used with any of the transducers previously
described or with any other compatible type of transducer.
In FIG. 9, housing 340 has internal threads 342 at one end to mate
with the threads 35 on the transducer and form a fluid-tight seal
up against the flange 36. A pair of spacers 346, 348 are formed on
the barrel of the housing to locate the current carrying coil 58.
The other end of housing 340 is thinned down and is threaded at 350
and fits within a cap 354 which also has threads 356 to receive the
threads 350.
A tubular sleeve 360 fits within the housing 340 and is of a size
to define an annular space 362 which forms a outflow passage for
the fluid. The interior portion of sleeve 360 defines a chamber 366
which surrounds the stack 10. The left end of sleeve 360 is formed
with a cylindrical section 370 which fits within a correspondingly
shaped bore 372 in the cap 354. An O-ring 374 located in a ring
depression on the section 370 provides a fluid seal between the
sleeve 360 and cap 354.
The cover sleeve 70 is internally threaded at 380 to mate with
threads 382 on the left end of cap 354. A hollow end cap 385 has a
reduced diameter section which is located within the rear opening
384 of the cover sleeve 70. End cap 385 is held against the left
end of cap 354 as the cover sleeve is threaded onto the cap 354.
The current carrying leads 59 for the coil 58 pass through the
opening in the end cap.
A fluid inlet conduit 390 passes through a bore in the cylindrical
section 370 of sleeve 360 to supply fluid to chamber 366. The fluid
exits from chamber 366 through passage 367 on the other end of
inner sleeve 360. The fluid, which has been heated by the stack,
flows back out through the annular passage 362 into a bore 357
through cap 354 in which is located an outlet conduit 359.
As seen, the housing structure of FIG. 9 provides both an inlet and
an outlet for the fluid. As in the case of the housing of FIG. 6,
the current-carrying coil is not in contact with the cooling fluid.
In both of the housing structures of FIGS. 6 and 9, the transducer
insert can be readily separated from the housing. There is no
physical electrical connection between the insert and the housing.
Further, in the case of FIG. 6, no additional tubes are needed to
supply fluid from the chamber to the workpiece.
* * * * *