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BACKGROUND OF THE INVENTION
The present invention is directed to a coupling member for a transmission
of shock waves from a shock wave source onto a patient to be treated.
In the field of medical diagnostic apparatus, which work with ultrasound,
it is known to couple the ultrasound applicator to the patient to be
examined by means of a coupling paste. Such a paste has a disadvantage
that air inclusions can occur at the boundary surface between the
applicator and the patient when the applicator is removed and reapplied.
These air inclusions lead to disturbances in the ultrasound image. It is
also known in this field to employ preliminary paths for the diagnostic
examination of patients and these paths have their speed of sound adapted
to that of the body tissue. These preliminary paths are generally formed
as containers, which include bags, sacks or the like, and are filled with
a liquid such as, for example, water. The container is usually coupled
with a coupling paste to the ultrasound oscillation exciter and to the
patient. In this way, disturbing reflections at the boundary surface of
the ultrasound applicator and also at the boundary surface of the
examination, subject can be avoided.
The invention is not related to an ultrasound diagnostic installation, but
rather to a shock wave therapy means, namely a means for disintegrating of
a concretions in the body of a life form. Such a means for disintegration
or disaggretation is disclosed, for example, in German OS No. 33 28 039
and in copending U.S. patent application Ser. No. 634,021, filed July 24,
1984, which application issued as U.S. Pat. No. 4,674,505 and claims
priority from German Patent Application No. 33 28 051. In this
disintegration device as well, a coupling paste has heretofore been
utilized for coupling and thus for transmitting shock waves on the path
from the shock wave source to the patient to be treated. Even when a
rubber-elastic member, for example as disclosed in German OS No. 33 12
014, a liquid-filled pillow, for example as disclosed in U.S. Pat. No.
4,539,989 which claimed priority from German Application No. 31 46 626, or
a liquid-filled accordion bellows, for example as disclosed in German OS
No. 33 19 871, was employed in such a disintegration device on this path,
a free-flowing coupling paste, nevertheless, had to be employed for
coupling these elastic component parts, at least on the side of the
patient. The use of such a coupling paste, however, requires a thorough
preparation of the patient before the actual therapeutic treatment and
also requires a careful cleaning of the patient, and under given
conditions of the shock wave apparatus as well after its use.
It would therefore be desirable if the coupling paste could be replaced
with a coupling member which, first, guarantees an acoustical reliable
coupling of the shock waves without gas inclusion at the boundary surface,
which makes involved cleaning after the treatment superfluous and which is
simple to handle in terms of manipulation.
A coupling member in the field of ultrasound wherein the first two demands
are met is disclosed in U.S. Pat. No. 4,459,854, which claims priority
from an application resulting in the U.K. Patent Application GB No.
2,102,657. The problem of manipulating of the gel compound is not
discussed in further detail in this reference.
SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to provide a coupling member
for a transmission of shock waves on the path from a shock wave source to
a patient which is to be treated, which coupling member guarantees a
reliable, reproduceable coupling, and which coupling is easy to manipulate
and guarantees clean work.
These objects are obtained in the invention in a coupling member which is
formed of an elastic, shape-stable material having moist outside surfaces,
and is provided with an insert which insert projects beyond the plastic
shape-stable material and forms means at the projecting part for grasping
the member.
The elastic, shape-stable material can preferably be a hydro-gel.
Hydro-gels are materials which contain water as a matrix. Such a hydro-gel
would, of course, also include gelatins. However, a polyacrylamide gel is
of particular advantage for use in the transmission of shock waves. Such a
material is extremely shape-stable, for example, easy to manipulate and
can be easily brought into a definite shape. During use, first it is
easily adapted to the contour of the patient's body, and secondly, to the
exit face of the shock wave generator.
The polyacrylamide gel for the coupling member is preferably synthesized
from:
(a) an Acrylamide (as a monomer);
(b) N, N'-methylene-bis-acrylamide (as a cross-linker);
(c) ammoniumpersulfate (as a catalyst);
(d) N, N, N', N'-tetramethylethylene-diamine (as a starter); and
(e) water (as a diluent).
The preparation is as thin-bodied as water. Arbitrary shapes of the
coupling member can be cast with this material. After polymerization has
been carried out, a transparent, soft elastic and relatively rip-proof gel
member having low attenuations for the shock waves and having an impedence
adapted to the human tissue is present. Hard-elastic through viscous gels
can be manufactured by modifying the monomer-to-water ratio.
Polyacrylamide gels are, for example, co-polymerisates of acrylamide and
methylene-bis-acrylamide, whose pore width is dependent on the graduation
between the monomeric and the cross-linked partners. The polyacrylamide
gels and receptors for their manufacture are known per se. In the prior
art, they are suitable as molecular sieves for separating, desalinizing
and concentrating substances having high molecular weight. For example,
they are also utilized in gel chromatography; and their manufacture can be
undertaken with commercially available raw materials in accordance with
known formulas, such as disclosed by H. Determann, Gelchromatographie,
Springer-Verlag, Berlin, Heidelberg, N.Y., pages 19-21 and page 31. Their
properties have been investigated in detail as set forth in Spektrum der
Wissenschaft, March 1981, pages 79-93. Polyacrylamide gels are also
employed for electrophoreus and suitable reagents are offered for this
purpose (see for example Desaga Katalog, Desaga Company, Heidelberg, pages
49 and 54).
The employment of an elastic, shape-stable material having moist outside
surfaces as coupling members guarantees an acoustically reliable coupling
without gas inclusions in the boundary surface. The coupling is
reproduceably good, for example, due to the dampness of the outside
surface, no disturbing air inclusions occur because of removal and
reapplication of the coupling member Such air inclusions can also be
easily perceived with the naked eye, given employment of an optical
transparent hydro-gel. The coupling is clean, for example, no
contamination of the apparatus and of the patient occurs when it is used.
As a consequence of the shape stability of the material employed and a
consequence of the enclosed insert, the coupling member is easy to
manipulate, for example, it is easy to transport, store and to adjust.
Hydro-gels are generally not expensive, and their disposal after use is
not involved.
The enclosure is preferably a non-metallic fabric or tissue, for example, a
material gauze which does not produce any defocussing or other noticeable
disruptions during treatment with shock waves. The insert projects
somewhat beyond the edge or side and is provided with means for grasping.
These means can, for example, comprise the overall projecting part or edge
is adequately wide in order to serve as a grasping surface during
manipulation. This is preferably true given a cylindrical-polygonal
shaping, for example a cuboid or cube shape. Instead, a grasping bracket
can also be provided at the projecting part or grasping means.
Another preferred embodiment is characterized in that the coupling member
is a coupling medium and preliminary path at the same time.
The coupling member can be fabricated in various thicknesses and can also
be adapted to the requirements in therapy. Hydro-gels and other equivalent
substances are usually non-toxic and are easily tolerated by the skin.
When a clear and transparent material is involved, which is preferred,
then the appertaining coupling location can be easily inspected.
During the operation of a shock wave source, for example of a lithotriptor
for disintegration of renal calculi, the shock wave pulse is generated
with the assistance of an electrical coil, such as disclosed by the
above-mentioned copending application and German OS No. 33 28 051, and
then checks of the function are appropriate from time to time. These
checks, for example, relate to the focus position, the pressure
distribution or the pressure amplitude of the shock wave pulse. Such
checks are regularly expedient in the use of the shock wave source;
however, they are also necessary given initial use after a rebuilding or
repair. When, for example, the means focussing the shock wave pulse, such
as for example acoustical lens or a reflector is replaced, then a
subsequent check must be carried out to see whether a focus position,
which is identical to the situation before the replacement, is still
present.
A shock wave sensor, which is in particular utilized for lithotripsy is
disclosed in German OS No. 34 37 976.
The specific embodiment of the invention under consideration here are based
on the consideration that both shock wave sensors, particularly electric
manometer elements, as well as shock wave indicators come into
consideration as check means for the function check. Given a shock wave
indicator, a subsequent evaluation, for example an estimate of the
integrally received energy, should be possible in addition to the
immediate observation of the point of incidence of the shock wave pulse.
The manipulability of the check means is of significance in addition to
the manufacturability and the price for the check. A coupling, which is
reproducible and loss-free is possible in a defined geometry, is also
important.
Another object of the invention is thus to construct a coupling member of
the species initially cited which, after the coupling, a simple check of
the function of the shock wave source is possible. In particular, it
should be possible to monitor the function of the shock wave source during
normal operation of the shock wave source, for example, during a
lithotripsy treatment.
The solution of this further object is characterized in that the shock wave
sensor is contained in the elastic, shape-stable material.
The shock wave sensor, which can be an electric manometer element, but can
also be utilized as a shock wave indicator, is preferably embedded in the
above-mentioned, shape-stable hydro-gel. All check means suitable for
measuring a shock wave fundamentally come into consideration as a shock
wave sensor, but particularly small electric manometers and small optical
indicators. The coupling members comprising a suitable shape such as, for
example, a disk or chunk shape can be put in place on the out-coupling
surface of the shock wave source by means of a support mount being put in
place therein in a defined relationship to the shock wave source. A good
coupling of the shock wave pulse to the shock wave sensor is an advantage.
The manipulation in checking the lithotriptor function is essentially
comprised of moistening one side of the coupling member, securing the
coupling member to the shock wave source and then performing measuring
procedure.
The transparent hydro-gel, which is preferably employed, enables a direct
observation or even an optical acquisition and evaluation of the front
side and/or back side of the shock wave indicator utilized as a sensor
without disassembly. If the shock wave sensor utilizes a piezo electric,
activated PVDF foil, then indications, which are produced by undesirable
movement of the measuring foil, are reduced.
Other advantages and objects will be readily apparent from the following
description, the claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional view of a first embodiment of a shock
wave therapy device utilizing a coupling member in accordance with the
present invention;
FIG. 2 is a schematic cross-sectional view of a second embodiment of a
shock wave therapy means having a concave shock wave exit surface with a
coupling member in accordance with the present invention;
FIG. 3 is a cross-sectional view of a coupling member having a frame or
band;
FIG. 4 is a cross-sectional view with portions in elevation for the purpose
of illustration with a modification of the same coupling member of FIG. 3
mounted on an end of a shock wave device;
FIG. 5 is a side view of a disc-shaped coupling member having a fabric
insert in accordance with the present invention;
FIG. 6 is a plan view of a cylindrical coupling member in an envelope type
of package;
FIG. 7 is a cross-sectional view of a framed coupling member in a
pot-shaped packing container;
FIG. 8 is a side view of a shock wave therapy means in accordance with the
present invention utilizing a coupling member having a fabric insert such
as illustrated in FIG. 5;
FIG. 9 is another type of shock wave means having a coupling member which
is held securely by means of clamping forceps;
FIG. 10 is a cross-sectional view of the arrangement of FIG. 9 illustrating
the clamping forceps employed therein;
FIG. 11 is a cross-sectional view with portions in elevation of a coupling
member including an integrated piezoelectric sensing device;
FIG. 12 is a cross-sectional view with portions in elevation of a shock
wave source and coupling member comprising an integrated PVDF foil given
capacity deviations for measuring signals;
FIG. 13 is a cross-sectional view of a coupling member having integrated
PVDF foil given galvanic deviations of the measuring signal; and
FIG. 14 is a shock wave source and coupling member comprising integrated
shock wave indicator.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The principals of the present invention are particularly useful when
incorporated in a shock wave therapy means generally indicated at 2 in
FIG. 1. The shock wave therapy means is specifically a disintegration
means for concretions such as, for example, renal calculi in a body of a
patient 4. The illustrated shock wave means 2 is known per se. It contains
a shock wave source 6, a lens 8 and a coupling medium 10, such as, for
example, water. The elements 6, 8, and 10 are accommodated in a housing 12
which is terminated at its output side by a membrane 14. The membrane 14
serves as a shock wave emission surface. The shock wave source 6 can be an
electro-magnetic means, such as, for example, what is referred to as a
shock wave tube, but can also be a piezo ceramic device. The shock wave
source has electrical terminals 15. The principal direction of the shock
wave focussed by the lens 8 is indicated by arrows 16.
A coupling member 20 is arranged between the exit membrane 14 and the
patient 4 to be treated. This coupling member 20 thus serves for the
transmission of shock waves on the path between the shock wave source 6 on
the one hand of the patient 4 on the other hand. The coupling member 20 is
formed of an elastic, shape-stable material 22 which is moist on all
sides, for example, has moist outside surfaces 24, 26 and as illustrated
has a essentially cylindrical shape.
The material 22 is preferably a material of a hydro-gel, such as a
polyacrylamide gel. Such a hydro-gel is viscous, elastic and its front and
back moist boundary surfaces 24 or, respectively, 26, easily adapt to the
membrane 14 or respectively to the patient 4. This material, thus, is not
like a paste, which is easily deformable and soft and which remains
adhering both to the membrane 14 as well as to the patient 4 after removal
of the coupling member. The matrix of the hydro-gel is water. The
impedence and speed of sound of the coupling member 20 can be set by a
greater or lesser addition of water during manufacture of the member 20.
As shown, the material 22 is rather shape-stable so that it can be
fundamentally used without an outside, rigid frame, such is shown later
with regard to FIGS. 3 and 4. However, it should be provided with an
insert as explained in greater detail with reference to FIGS. such as 5, 6
and 8. The material 22 of the coupling member 20 is cross-linked so that
it is essentially homogeneous.
In FIG. 2, a different shape and form for the shock wave therapy means or
device is indicated at 2a. This shock wave therapy means 2a is equipped
with a focussing shock wave source. It can be either a piezo electric
member having a calotte-shaped or spherical emission surface or, as shown,
can be a shock wave tube having a concave coil and a calotte-shaped
emission member in the form of a membrane 28. The latter embodiment of a
shock wave tube comprises a concave emission surface is illustrated and is
described, for example in German Utility Model No. 84 13 031. A coupling
member, generally indicated at 20a, of an elastic, shape-stable material
22 which again has moist outside surfaces 24a and 26 is again mounted
between the emission surface 28 and the patient 4. In this embodiment, the
coupling member, which is again preferably composed of a hydro-gel, meets
two functions, first it serves as a preliminary path, and second, it is
used as a coupling medium as a consequence of its moist outside surfaces
24a and 26.
An embodiment of the coupling member is generally indicated at 20b in FIG.
3, and essentially is a cylindrical shape which is framed on its edges. A
flexible hose piece or band 30, for example, a silicone hose piece, is
provided for the frame. This has a width d which is matched to the
application and to the coupling member 20b. Various coupling members 20b
having different thicknesses can be kept on store for routine
examinations. As shown, the two coupling surfaces 24 and 26 at the ends
are convexly shaped. Given employment between a shock wave exit surface
and patient, they can be deformed to a greater or lesser degree. A
hydro-gel is again employed here as the material 22. This is characterized
by a low attenuation for the shock waves. The impedence and speed of sound
of this medium can be adapted to the body tissue. It should be pointed out
as an advantage that both the hose piece 30, as well as the material 22,
are transmissive to x-radiation and this enables a locating of the
concrement with the coupling member 20b in place.
In a modification of the coupling member is generally indicated at 20b' in
FIG. 4 and has a ring 32 for framing the member. The ring 32 is fabricated
of a semi-hard material, which is x-ray transmissive. It can be slipped
onto the corresponding shaped cooperating member 34 which is connected to
the shock wave source (not shown). This cooperating member 34 can, in
particular, be a coupling bellows having a known design.
Such a coupling bellows is inflatable in order to set the focus of the
disintegration means in a fine regulation or setting. The ring 32 and the
material 22 can be kept on hand in various thickness; in this way, a
compensation of various thicknesses of the patient examined can be
produced. Departing therefrom, only the material 22 fashioned wafer-like
can be kept on hand in various thicknesses in order to change it and the
ring 32 dependent on the patient thickness.
Another embodiment of the coupling member is indicated at 20c in FIG. 5 and
has a shape of a thin disk and is provided with a planar insert 38. This
insert 38 is a coarse-weave fabric, such as a gauze, composed of an x-ray
permeable material, for example a textile weave. The integration of this
fabric serves to increase the mechanical stability and to facilitate the
manipulatability of the coupling member 20c. The fabric insert 38 can
proceed through the center of the disk and extends perpendicular to the
direction of the maximum radiation indicated by the arrow 16. However,
there is also applications wherein the embedding of the fabric insert 38
in the proximity of one of the two coupling faces 24 and 26 is more
advantageous. As shown in FIG. 5, the insert 38 projects beyond the edges
of the elastic, shape-stable material 22 on all sides. It can be grasped
on these extended portions and the exposed edges of the insert 38 thus
serve as means for increasing the manipulability, for example in an
adjustment.
A modification of the coupling member is generally indicated at 20c' in
FIG. 6 and shows an interposed insert 38' which is provided with a
grasping bracket or projection 40. The overall coupling member 20c' is
illustrated as being in a packet 42. This packet or packaging can be a
transparent envelope having a rectangular construction which is closed in
an air-tight fashion. The envelope can be composed of a plastic bag of,
for example, polyethylene which is equipped with a thin metallization.
This plastic bag is bonded in an air-tight fashion and thus forms a
container. The coupling member 20c' is protected against drying out in
this manner. It can be transported and stored over long periods of time in
the container or package 42. The coupling member 20c' is not removed from
the package 42 until immediately before use. This removal can be
facilitated by tear seams 44 and 46 which are provided along two adjacent
edges of the package 42.
In FIG. 7, a coupling member 20b' is illustrated as being stored in a
pot-like container 50 which is closed air-tight. This container 50 is
composed of a small pot 52 having a bent-over peripheral flanged edge to
which a transparent foil 54 is bonded. A plastic-coated metal foil can
also be used instead of the transparent foil 54. The foil 54 is provided
with a rip clip or rip seam 56. The structure of the container 50 is
similar to that used for cups of food such as a yogurt cup.
As illustrated in FIG. 8, a gel-like coupling member 20c which has an
insert 38 is held fast between the shock wave exit face in the form of the
membrane 14 and the patient 4. The projecting edges of the embedded insert
38 serve the purpose of fastening the coupling member 20c to a shock wave
source of a shock wave therapy means 2c. This fastening is indicated by
two retaining pins 58 and 60 and fastening buttons or clips 62 and 64,
respectively, which are engaged therewith. Any other type of fastening can
be fundamentally selected.
In FIGS. 9 and 10, the coupling member 20c is illustrated without the
insert 38 for purposes of clarity. As illustrated in these figures, two
clamping forceps 70 and 72 are provided for securing the coupling member
20c to a shock wave therapy means 2d which has a shock wave source. In
certain applications, a single, broad clamping forceps 70 will be
sufficient. The second clamping forceps 72 serves the purpose of adapting
to different thicknesses of the coupling member 20c.
As illustrated in FIG. 10, the two clamping forceps 70 and 72 are shaped in
the fashion of clothespins and they comprise essentially hemispherical
clamping legs 82 and 84 which are connected to manipulation legs or
handles 88 and 90, respectively, through a rotational axis 86. A spreading
spring such as 92 exerts a framing pressure on the coupling member 20c in
a clamped condition and lies between the two manipulating legs 88 and 90.
For removing the coupling member, the two manipulation legs 88 and 90
merely have to be pressed toward one another.
As clearly illustrated in FIG. 9, the first clamping forceps 70 is secured
to a support mount 94 which in turn is attached to the shock wave therapy
means 2d. This support mount 94 can essentially comprise a pipe in which a
rod 96 is displaceable in a longitudinal direction. The second clamp
forcep 94 is secured to this rod 96. The displaceability in the
longitudinal direction is indicated by the double arrow 98. In order to
lock the second clamping forcep 92 and the rod 96 in a determined
position, a clamping means 100', for example a clamping screw, is provided
at the support mount 94. After the adjustment, this prevents a dislocation
of the rod 96 in the direction of the double arrow 98 so that the coupling
member 20 is effectively fixed in front of the concave emission surface
which may be formed by a membrane 28. The coupling member 20c can then
easily and quickly be replaced for another coupling member having a
different thickness, and this is accomplished by means of releasing the
two clamping forceps 70 and 72.
It should be mentioned that the illustrated disintegration means discussed
hereinabove can be an ultrasound applicator which is used in the field of
ultrasonic diagnosis. Thus, the coupling means, or member, can be utilized
with either a device for diagnosis as well as for disintegration.
In FIG. 11, a shock wave source generally indicated at 100 is shown with
its essential elements comprising a shock wave generator 103, a
preliminary path 105 with a focussing means or arrangement and an
out-coupling membrane 107. A coupling member 111 is supported by a
hollow-cylindrical mount 109, and is applied to the out-coupling surface
or membrane 107. This coupling member 111 is composed of an elastic,
shape-stable material particularly of a hydro-gel having moist surfaces. A
patient 113 is coupled to the free end face of a coupling surface 112 of
the concavo-convex coupling member 111. The coupling member 111 serves for
the transmission of shock wave pulses from the shock wave source 103 to
the patient 113. This arrangement has already been set forth in detail
with reference to FIGS. 1-10.
The coupling member 111 contains a shock wave sensor 115. In the
illustrated embodiment, the shock wave sensor 115 is an electrical sensor,
specifically a piezo ceramic or piezo crystal 117 which is connected to a
measuring instrument 121 via leads 119. The piezo crystal 117 is
preferably arranged in a center region of the middle of the coupling
member 111, for example on the central axis 122 of the shock wave source
103. It is also possible to provide a plurality of piezo electric crystals
next to one another, namely in a radial direction with reference to the
central axis 122 or on a ring around the central axis 122.
In normal operations of the shock wave generator 103, for example during
lithotripsy treatment of a patient 113, the function of the shock wave
source or generator 103 can be continuously checked with the assistance of
the piezo crystal 117 and the measuring instrument 121. The check is
composed, for example, of monitoring the correct, i.e., prescribed,
pressure amplitude of the shock wave pulse at the location of the shock
wave sensor 115. By utilizing reference measurements previously undertaken
at the work side, it is known that the prescribed amplitude of the shock
wave pulse or reference value must occur at the location of the shock wave
sensor 115 given proper operation and proper positioning under prescribed
operating parameters. For example, an operating voltage of 15 kV, a
capacitor capacitance of 0.5 .mu.F, a preliminary path length of 20 cm,
etc. When, during the on-going course of therapy treatment, which can
comprise up to 1000 shock wave pulses per patient, the pressure amplitude
identified by the shock wave sensor 115 differs from the reference value
by a prescribed percentage, then it is evident that there is a possible
malfunction of the shock wave generator 103. The identification of the
elevated pressure amplitude can then be used in order to interrupt the
therapy treatment and too low a pressure amplitude can likewise be a
reason for interrupting the therapy treatment and for carrying out a
subsequent inspection of the device. Over and above this, the shock wave
source 103 can be recalibrated or reset with the shock wave sensor 115
integrated in the coupling member 111 after any repairs or maintenance.
When, for example, an electromagnetic flat coil is utilized in a known way
as a shock wave generator 103, and this has been replaced by another coil
during maintenance, there is the possiblity that the center of the new
coil is slightly dislocated. Consequently, the anticipated reference
values will not occur given incidence of a shock wave pulse at the shock
wave sensor 115 but only a lower value will occur. The coil can be
readjusted until the prescribed reference value is obtained. It is then
assured that the shock wave means 100 will then have the same property as
it had before the maintenance or repair.
The reference value, which is used for readjustment of the shock wave
device 100, need not be the same as in what is referred to as an on-line
operation with the patient 113. For example, the operating parameters of
the voltage value can amount to only 12 kV instead of the said 15 kV in a
therapy treatment and can traverse a range from, for example, 12 kV
through 20 kV.
An embodiment of the shock wave device or means is generally indicated at
100a in FIG. 12. The device 100a has a shock wave source or generator 103
with a preliminary path 105, which contains desired focussing means and an
out-coupling membrane 107a. A coupling member 111a, which has an embedded
metal membrane 130 engages an outer surface of the coupling membrane 107.
As illustrated, the membrane 130 has its peripheral edges or portions
clamped by externally disposed supports 109a of the device 100a. The metal
membrane 130 has a recess or opening 132 at its center which is coaxially
relative to the center axis 122 of the shock wave generator 103. The
recess 132 is spanned by a partially piezo electric foil, for example a
PVDF foil 134, which is piezo electrically activated, for example
polarized, in its central region. An annular diverter electrode 136, which
is arranged outside of the polarized area is provided at each of the two
sides of the PVDF foil 134. The diverter electrodes 136 are connected by
lines 119 which lead to a measuring instrument 121. The PVDF foil 134 and
the annular diverter electrodes 136 form a shock wave sensor 115a in this
embodiment. The shock wave sensor 115a is set forth in detail in German
Application P No. 35 45 382.6, which was the basis of U.S. Ser. No.
937,840 , Filed Dec. 4, 1986, which issued as U.S. Pat. No. 4,734,611 on
Mar. 29, 1988 and whose contents are incorporated by reference there | | |
