U.S. patent number 3,663,933 [Application Number 05/052,038] was granted by the patent office on 1972-05-16 for protective band for bilaminar transducer with slotted spacer ring.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Theodore C. Madison.
United States Patent |
3,663,933 |
Madison |
May 16, 1972 |
PROTECTIVE BAND FOR BILAMINAR TRANSDUCER WITH SLOTTED SPACER
RING
Abstract
An improvement in bilaminar sonar transducers which employ
slotted, complt, outer spacer rings, the improvement comprising
filling the slots with a plastic resin, such as epoxy resin, having
a low modulus of elasticity as compared with that of the spacer
ring, and banding the spacer ring with a wrapping of fiberglass
tape which is impregnated with epoxy resin and cured.
Inventors: |
Madison; Theodore C. (Santa
Barbara, CA) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (N/A)
|
Family
ID: |
21975028 |
Appl.
No.: |
05/052,038 |
Filed: |
July 2, 1970 |
Current U.S.
Class: |
367/141;
310/331 |
Current CPC
Class: |
B06B
1/0611 (20130101); B06B 1/0677 (20130101) |
Current International
Class: |
B06B
1/06 (20060101); G01v 001/16 () |
Field of
Search: |
;340/8R,8C,8MM,8L,8D,8PC,8FT,8S,10 ;310/8.2,8.4,8.7,9.1,9.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Benjamin A.
Assistant Examiner: Tudor; H. J.
Claims
I claim:
1. In a bilaminar sonar disc transducer having a crystal backing
assembly comprising a pair of metallic discs separated by a slotted
metallic peripheral spacer ring, the improvement comprising:
a filling for said slots from a material having a low modulus of
elasticity compared to that of said slotted, metallic spacer ring;
and
a protective band wrapped around the outside of said spacer ring,
said band comprising at least one layer of tape impregnated with a
plastic resin, the density of said tape and resin being
sufficiently low that the radial compliance of the combination is
at least an order of magnitude below that of said slotted spacer
ring.
2. A transducer as in claim 1, in which said tape is fiber glass
tape.
3. A transducer as in claim 1, in which said filling and said
tape-impregnating materials are epoxy resins.
4. A transducer as in claim 1, in which said tape is fiber glass
tape, and said filling and tape-impregnating materials are plastic
resin.
5. A transducer as in claim 1, in which said tape is fiber glass
tape, and said filling and tape-impregnating material are epoxy
resin.
Description
The invention described herein may be manufactured and used by or
for the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or
therefor.
BACKGROUND OF THE INVENTION
This invention relates to bilaminar sonar transducers and
especially to a protective band for the compliant spacing ring of a
bilaminar transducer.
Slots in the spacing ring of a bilaminar transducer are designed to
provide a high radial compliance to the transducer assembly, high
compliance being a necessary condition for a maximum coefficient of
electromechanical coupling, minimum mechanical stress, maximum
radiation resistance and maximum output power capability. These
slots, however, leave thin sections of metal in the spacer ring and
the thin sections of metal are subject to failure, even under low
hydrostatic pressure.
STATEMENT OF OBJECTS OF THE INVENTION
Accordingly, an object of this invention is to provide the
compliant spacer with protection against failure due to hydrostatic
pressure while substantially maintaining the high compliance of the
spacer.
This and other objects and advantages result from filling the slots
in the spacer ring with a low-modulus resin and banding the spacer
ring with one or more layers of tape consolidated with a resin, the
overall compliance of the filling and wrapping structure being high
enough not to significantly affect the performance of the flexural
disc assembly but having sufficient stiffness and strength to
prevent failure of the slots due to hydrostatic pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, advantages and novel features of the invention will
become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings wherein:
FIG. 1 is an isometric view of the crystal backing assembly for a
bilaminar sonar transducer;
FIG. 2 is an isometric view of a bilaminar sonar transducer;
FIG. 3 is an isometric view of a bilaminar sonar transducer after
the spacer ring has been wrapped with fiberglass tape;
FIG. 4 is a partially sectioned side view of a crystal backing
assembly; and
FIG. 5 is a partially sectioned side view of an embodiment of the
invention .
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows the crystal backing assembly of the typical bilaminar
sonar disc transducer. This component consists of an upper and a
lower metallic disc 10 and 11 separated by a spacer ring 12 around
the circumference of the discs which are positioned in parallel,
i.e., one above the other. The material from which the discs and
spacer ring are fabricated may be stainless steel, for example. The
discs are welded to the spacer ring, the welds 24 being shown in
FIG. 4.
The spacer ring 12 has slots 14 therein at spaced intervals and
thicker segments 22 between the slots. The welding provides a zero
bending moment at the edges of the metal discs and the slots
provide a high degree of radial compliance. However, the slots also
give thin metal areas which are subject to hydrostatic pressure
failure.
To prevent this pressure failure, the slots 14 are filled with a
material which has a low modulus of elasticity compared to that of
the spacer ring 12. This material may, for example, be an epoxy
resin. The filled slots 15 are shown in FIG. 2 which, except for
the filling in the slots, illustrates a typical bilaminar disc
transducer having upper and lower ceramic discs 16 and 17 affixed
to the outer surfaces of the upper and lower metallic discs 10 and
11 of the crystal backing assembly (see, also, FIG. 5).
The upper and lower surfaces of each ceramic disc are coated with a
thin metallic coating which comprises an electrode. The
outer-surface electrodes are electrically interconnected by wire 19
and the inner surface electrodes are electrically interconnected by
wire 21, and lead wires 18 and 18' are brough out as shown in FIGS.
2 and 5.
Since filling the slots 14 is not sufficient in itself to
completely protect the transducer against external pressure, the
spacer ring 12 is banded by wrapping one or more layers of
plastic-impreganted tape around it. This band 20 may consist of
fiber glass tape impregnated with a plastic resin such as that used
to fill the slots 14. The resin may, for example, be the product of
the Shell Chemical Corporation designated Epon 815. The fiber glass
filaments span the filled slots and provide the extra strength
needed to protect the unit against hydrostatic pressure. The
density of the fiber glass tape and resin is still low enough that
the radial compliance of the impregnated tape is at least an order
of magnitude below that of the metal spacer ring.
The resin is cured by the proper heat treatment for the particular
type of resin which is used.
Obviously many modifications and variations of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *