Information
-
Patent Grant
-
6217531
-
Patent Number
6,217,531
-
Date Filed
Monday, October 26, 199826 years ago
-
Date Issued
Tuesday, April 17, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Lateef; Marvin M.
- Shaw; Shawna J.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 600 439
- 367 146
- 367 147
-
International Classifications
-
Abstract
The present invention relates to a electrode assembly and related method that includes a insulator assembly, an electrode assembly, a charging system, a mechanism for measuring electrical voltages, a mechanism for adjusting the distance between inner and outer electrode tips, and a controller. The insulator assembly includes an insulator body having a hollow central portion with a threaded inner wall. The insulator assembly includes inner and outer conductors that are electrically connected to the charging system and are physically connected to inner and outer electrodes, respectively. The electrodes are positioned such that their longitudinal axes are aligned and the tips of the electrodes are in relatively close physical proximity. The distance between the tips is defined as the spark gap. The charging system charges a capacitor that discharges and forms a spark across the spark gap. The electrical measuring mechanism measures the discharge voltage of the capacitor and the controller compares it to a reference voltage, issuing a correction signal to the adjusting mechanism that repositions the electrodes, thus optimizing the spark gap. An alternate embodiment analyzes the charge and discharge characteristics of an electrode assembly that utilizes a second capacitor and an inductor to adjust the spark gap.
Description
BACKGROUND OF THE INVENTION
The present application claims foreign priority based on German application 197 46 972 filed on Oct. 24, 1997.
1. Field of the Invention
The present invention relates to the area of lithotripters; more particularly, a lithotripter electrode having an automatically adjusting spark gap.
2. Description of Related Art
Lithotripters exist for the contact-free destruction of concrements, e.g. kidney stones, in living bodies. Such devices are also used for the treatment of orthopedic ailments such as heal spurs and tennis elbow as well as non-union of bone problems. Lithotripters and related hardware are described in a number of patents; all of those mentioned below are hereby incorporated by reference.
Lithotripters use an electric underwater spark to generate the shock waves necessary to effect treatment. The spark is generated by an electrode usually mounted in a reflector that is used to focus the shock waves. Examples of these attempts may be found disclosed in U.S. Pat. Nos. 4,608,983 and 4,730,614.
In general, shock wave generation uses a spark produced by a discharge between electrodes. The discharge across the spark gap results from the discharge of an electrical capacitor. Varying the amount of the charging voltage of the capacitor regulates the shock wave energy. A larger or smaller voltage results in the formation of a stronger or weaker spark and thus modifies the strength of the shock wave and the size of the therapeutically active focus and thus in turn the applied shock wave energy.
It is desirable to provide a broad energy spectrum because of the various energy levels of shock waves used to treat different ailments. However, the voltage cannot be varied at will without replacing the electrode assembly because the spark gap, the gap between the electrodes, controls the discharge process. A wider gap requires a larger minimum voltage to bridge the distance between the two electrodes with a spark.
Early lithotripter electrodes used a fixed spark gap. One disadvantage to a fixed-gap electrode is that the electrodes slowly burn away after repeated use, thus increasing the spark gap distance and requiring a greater amount of voltage to generate a spark. But the larger gap and larger minimum voltage produces a stronger shock wave. One invention intended to resolve the electrode burn off issue is disclosed in U.S. Pat. No. 4,809,682.
Another disadvantage is that a low energy shock wave requires a low amount of voltage to be used with a relatively narrow spark gap while a high-energy shock wave requires a large amount of voltage to be used with a relatively wide spark gap. Accordingly, low energy shock waves could not be generated immediately following treatment using high-energy shock waves and vice versa without wholesale replacement of the electrode assembly. If an electrode assembly with a relatively small spark gap is used with a higher voltage, an energy-inefficient spark is produced because a portion of the energy bleeds off into the surroundings and is transformed into acoustic energy while another portion is transformed into heat energy and does not contribute to the formation of the shock wave. In other words, the proper voltage applied to the capacitor must be matched with a proper spark gap to produce an efficient shock wave of the desired energy level.
Another disadvantage with some lithotripter electrode assemblies is the inability to easily exchange one set of electrodes for another. For example, if the electrodes are to be reconditioned or refurbished, electrodes that are permanently attached cannot be removed and replaced.
Subsequent to the disclosure of fixed-gap electrode assemblies, adjustable gap assemblies were invented to overcome the difficulties associated with fixed-gap assemblies. One type, as disclosed by Patent EP 0.349.915 suffers from the disadvantage that it must be adjusted manually; another type, disclosed in U.S. Pat. No. 4,730,614 can only be adjusted in one direction.
Accordingly, there remains a need for an improved, self-adjusting lithotripter electrode assembly that allows a variety of energy levels to be employed, compensates for electrode bum-off, and increases the overall life of the electrode assembly.
SUMMARY OF THE INVENTION
The present invention relates to medical treatment using shock wave therapy and related method; more particularly, a self-adjusting lithotripter electrode assembly. The preferred embodiment of the electrode assembly includes an insulator assembly, an electrode arrangement, a charging system, a mechanism for measuring electrical voltages, a mechanism for adjusting the distance between inner and outer electrode tips, and a controller. The insulator assembly includes an insulator body having a hollow central portion with a threaded inner wall. The insulator assembly also includes inner and outer conductors that are electrically connected to the charging system and are physically connected to inner and outer electrodes, respectively. The electrodes are positioned such that their longitudinal axes are aligned and the tips of the electrodes are in relatively close physical proximity. The distance between the tips is defined as the spark gap. The charging system includes a capacitor and a voltage source. The electrical measuring mechanism includes a conventional meter device. The controller includes a microprocessor, microcomputer, or equivalent device.
The operation is as follows. A voltage is applied to the capacitor that is charged at a constant rate. When the voltage reaches a certain level, a spark is produced across the spark gap as the capacitor discharges. The electrical measuring device measures the actual discharge voltage and a corresponding signal is sent to the controller. The controller then compares the discharge voltage to an optimum, i.e., reference, discharge voltage. If the spark gap is correctly adjusted, the discharge of the second capacitor is at its maximum voltage and no correction is made. However, if the spark gap is too narrow, the discharge of the second capacitor occurs before the capacitor has achieved its maximum value. If the spark gap is too wide, there is either only a partial discharge after the capacitor has reached its maximum value or no discharge at all. In either case, the spark gap is not set to its optimum distance, resulting in an incomplete use of the energy stored in the capacitor. Accordingly, the controller issues a correction signal to initiate a spark gap adjustment, thus actuating the motor and associated components. The motor engages the gearbox that in turn moves the threaded element forward or rearward, thus positioning the inner conductor and the inner electrode such that the spark gap is of a distance capable of producing a spark at the optimum or reference voltage.
An alternate embodiment utilizes an additional capacitor and an inductor. The discharge of the first capacitor does not take place directly across the spark gap, but instead discharges to a second capacitor that is directly connected to the electrode conductors. When the voltage from the second capacitor reaches a sufficient value, a spark is then created across the spark gap. The controller compares the charge and discharge characteristics of the second capacitor. If a discrepancy exists between the actual discharge voltage and the reference discharge voltage, the controller computes the proper spark gap and issues a signal to the motor, which results in a spark gap adjustment as described above.
One advantage of the present invention includes a solution to the electrode burn-off problem by automatically maintaining a proper spark gap.
Another advantage of the present invention includes the ability to provide a wide spectrum of energy levels without the necessity of replacing the electrodes.
Still another advantage of the present invention includes the ability to easily replace the electrodes when needed.
Yet still another advantage of the present invention includes the elimination of manual adjustment of the spark gap.
Yet still another advantage of the present invention includes the ability to both widen and narrow the spark gap.
Additional advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, which exemplifies the best mode of carrying out the invention.
The invention itself, together with further objects and advantages, can be better understood by reference to the following detailed description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A
is a system diagram of the preferred embodiment of the present invention.
FIG. 1B
is an enlarged side elevational view of the electrode assembly of the present invention.
FIG. 1C
is a forward end view of the electrode assembly shown in FIG.
1
B.
FIG. 2
is an electrical schematic of an alternate embodiment of the present invention.
FIG. 3A
is a graph of the voltage experienced over time of the first capacitor of the alternate embodiment shown in FIG.
2
.
FIG. 3B
is a graph of the voltage experienced over time of the inductor of the alternate embodiment shown in FIG.
2
.
FIG. 3C
is a graph of the voltage experienced over time of the second capacitor of the alternate embodiment shown in FIG.
2
.
FIG. 4A
is a graph of the voltage experienced over time of the second capacitor of the alternate embodiment shown in
FIG. 2
, including a voltage offset.
FIG. 4B
is a graph of the integral of the voltage experienced over time of the second capacitor of the alternate embodiment shown in FIG.
2
.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Referring now to
FIGS. 1A-1C
, the preferred embodiment of the electrode assembly
100
, which has a forward end
101
and a rearward end
102
, includes a insulator assembly
200
, an electrode arrangement
300
, a charging system
400
, a mechanism
500
for measuring electrical voltages, a mechanism
600
for adjusting the distance between inner and outer electrode tips, and a controller
700
.
The insulator assembly
200
includes an insulator body
201
that is cylindrical in construction having a hollow central portion
201
a
. The insulator
201
has a threaded inner wall
202
. The insulator
201
is mounted in a focusing device
900
, the focus device
900
having an outer wall
901
with an opening
901
a
through which the insulator
201
is partially disposed. The insulator
201
also includes an outer locking ring
215
, an inner locking ring
220
, and a seal
225
, best shown in FIG.
1
B.
The insulator assembly
200
further includes an inner conductor
205
and an outer conductor
210
. The inner conductor
205
is a rod-like component that is slidably positioned within the central portion
201
a
of the insulator body
201
as shown in FIG.
1
B. In the preferred embodiment, the inner conductor
205
has a threaded forward end
206
for engaging an inner electrode
305
, described in further detail below. The inner conductor
205
is made of an electrically conductive metal or equivalent material. The outer conductor
210
surrounds the insulator body
201
and is made of a material similar to or identical to that of the inner conductor.
The electrode arrangement
300
includes an inner electrode
305
and an outer electrode
310
. The inner electrode
305
is a short, rod-like component and has a tapered tip
306
and a threaded rearward end
307
. It is coaxially affixed to the inner conductor
205
via the threaded end
307
engaging the threaded end
206
of the inner conductor
205
as shown in FIG.
1
B and is partially disposed within the insulator
201
. Alternately, the inner electrode
305
may be soldered to the inner conductor
205
or attached in a similar manner. The inner electrode
305
is made of an electrically conductive metal or equivalent material and is electrically connected to the inner conductor
205
.
The outer electrode
310
is a short, rod-like component and also has a tapered tip
311
. The outer electrode
310
is supported by the outer electrode cage members
312
, each of which includes a hook
313
that is formed at a generally right angle to the cage member
312
. The outer electrode cage members
312
are J-shaped at the forward end, best shown in
FIG. 1B
, to help alleviate the stress caused by the high voltage. The outer electrode
310
is mounted to the insulator
201
at the forward end
101
of the electrode assembly
100
as shown. The outer electrode
310
is usually attached to the outer electrode cage
312
by a soldering process or equivalent. The outer electrode
310
is positioned such that the longitudinal axes of the inner and outer electrodes
305
and
310
are aligned and the tips
306
and
311
of the electrodes
305
and
310
are in relatively close physical proximity. The distance D between the tip
306
of the inner electrode
305
and the tip
311
of the outer electrode
310
is defined as the spark gap
315
.
The charging system
400
includes a high voltage switch
401
, typically a thyratron in the preferred embodiment, and a capacitor
405
that is a high-voltage variety of standard construction. It is electrically connected to the inner and outer conductors
205
and
210
. The capacitor
405
is also electrically connected to a voltage source (not shown) and the controller
700
as shown in FIG.
1
A.
The device
500
for measuring electrical voltages is a conventional electrical meter (not shown) or equivalent. It may be an integral part of the controller
700
, described below, or may be a separate unit.
The mechanism
600
for adjusting the spark gap
315
includes a motor
605
, a gearbox
610
, and a threaded element
615
having threads
616
. The motor
605
is mechanically connected to the gearbox
610
that in turn is mechanically connected to the threaded element
615
. The threaded element
615
is partially disposed within the rearward end of the insulator
201
such that the threads
616
on the outer surface of the threaded element
615
engage the threaded inner wall
202
of the insulator
201
at the rearward end
102
of the electrode assembly
100
. Alternately, the inner conductor
205
and the threaded element
615
may be a formed as a single integral component.
The controller
700
typically includes a microprocessor, microcomputer, or other like device (not shown) capable of performing at least complex mathematical and comparative functions. The controller
700
is electrically connected to the motor
605
and the capacitor
405
and
410
.
One feature of the present invention includes the ability to quickly change electrodes for reconditioning or other maintenance. First, the outer locking ring
215
is moved in the rearward direction. The inner locking ring
220
is also moved in the same direction, thus allowing the outer electrode cage hooks
313
to disengage from the groove
210
a
in the insulator body
210
. The outer electrode
310
and cage
312
is then pulled away from the electrode assembly
100
. With the outer electrode
310
and cage
312
out of the way, the inner electrode
305
may be unscrewed from the inner conductor
205
. New electrodes may then be easily installed with the hooks
313
of the new cage
312
engaging the groove
210
and locking rings
215
and
220
and spacer
225
frictionally retaining the hooks
313
in place.
The operation of the electrode assembly
100
of the present invention is as follows. A voltage V is applied to the capacitor
405
, which is charged at a constant rate. When the voltage reaches a certain level V
d
, a spark is produced across the spark gap
315
as the capacitor
405
discharges. The actual discharge voltage V
d
is measured by the electrical measuring device
500
and a corresponding signal is sent to the controller
700
. The controller
700
then compares the discharge voltage V
d
to an optimum, i.e., reference, discharge voltage V
dref
. If a discrepancy exists between the actual discharge voltage V
d
and the reference discharge voltage V
dref
, the controller
700
computes the proper spark gap
315
and issues a signal to the motor
605
. The motor
605
engages the gearbox
610
that in turn moves the threaded element
615
forward or rearward, thus positioning the inner conductor
205
and the inner electrode
305
such that the spark gap
315
is of distance capable of producing a spark at the optimum or reference voltage V
dref
.
In an alternate embodiment of the present invention, a second capacitor
410
is used that is electrically connected in series with the first capacitor
405
with an inductor
415
in between the two capacitors
405
and
410
as shown in the electrical schematic FIG.
2
. The high voltage switch
401
used is a thyratron or equivalent. The controller
700
is also connected to the second capacitor
410
.
FIGS. 3A-3C
are voltage vs. time graphs that depict the operation, that is, the sequence of electrical events, during the formation of a spark in the alternate embodiment. A voltage V is applied to the capacitor
405
that is charged at a linear rate over time t
1
, depicted by curve portion
10
. The controller
700
, via line
498
as shown in
FIG. 2
, monitors the charging of the capacitor
405
. The maximum load of the capacitor
405
is reached at point
11
and remains constant, i.e., fully charged over time t
2
, depicted by curve portion
12
. At a time certain, point
11
, the switch
401
is actuated and a controlled discharge is initiated, depicted by curve portion
14
.
As the voltage from the first capacitor
405
is discharged, the voltage experienced by L
1
begins to increase, as depicted by curve portion
20
in FIG.
3
B and the second capacitor
410
begins to charge, depicted by curve portion
30
in
FIG. 3C
, both occurring over time period t
3
. At the end of time period t
3
, the voltage experienced by L
1
reaches its maximum, V
C1max
, shown as point
21
in FIG.
3
B and the curve portion
30
in
FIG. 3C
reaches a point of inflection
31
, i.e., the point where the slope of the curve
30
changes from positive to negative.
During time period t
4
, the voltage experienced by the inductor
415
drops off as shown by curve portion
22
in
FIG. 3B
; the capacitor
410
continues to charge as shown by curve portion
32
, although the rate of charge is decreasing. As the voltage experienced by the inductor
415
reaches zero at the end of time period t
4
, the voltage V
C2max
of the second capacitor
410
reaches its maximum value as depicted by point
34
in FIG.
3
C and the second capacitor
410
is fully charged. It is at this point, ideally, that the second capacitor
410
should discharge and a spark should form, as depicted by curve portion
36
. A spark formed at this point in time indicates that the spark gap
315
is at its optimum distance D and that all the energy in the second capacitor
410
is being used to form the spark. A spark that is produced before point
34
in
FIG. 3C
is reached indicates that the spark gap
315
is too narrow; a spark that is produced after point
34
is reached indicates the spark gap
315
is too wide. Generally speaking, a spark that is produced at between 90% and 100% of the second capacitor's maximum voltage V
C2max
is considered acceptable. In other words, a spark produced in the hatched region A between curve portions
37
and
38
is considered acceptable for the present invention, although acceptable error parameters can be varied. The controller
700
, via line
499
as shown in
FIG. 2
, monitors the charging and discharging of the capacitor
410
.
If the spark gap
315
is much narrower than optimum, then a spark will be formed prior to the voltage curve reaching 90% of the maximum, V
C2(.9)
value, shown by point
33
in FIG.
3
C. In such a case, the controller
700
issues a correction signal to the motor
605
and the spark gap
315
would be adjusted (made wider) by the method described above. If, on the other hand, the spark gap
315
is much wider than optimum, then either a) a spark will be formed subsequent to the voltage curve dropping off 90% of the maximum, V
C2(.9)
value, shown by point
35
in
FIG. 3C
, or b) no spark will be produced at all, as shown by curve portion
39
in FIG.
3
C. In such a case where the spark gap
315
is much too wide, the controller
700
issues a correction signal to the motor
605
and the spark gap
315
would be physically adjusted (made narrower) by the method described above.
To increase the accuracy of the correction process described above, it is possible to examine a series of charges and discharges before making a spark gap correction, as opposed to examining only one charge and discharge cycle prior to making a correction. The controller
700
is programmed to analyze a predetermined number of charges and discharges prior to making a determination. The series is then statistically analyzed and only then is a correction made, if necessary. Thus, a single false voltage measurement or other glitch would not result in an unnecessary correction that would ultimately have to be recorrected.
As discussed above, it is possible to determine the optimum spark gap
315
by examining the charge and discharge voltage characteristics of the second capacitor. However, an even more accurate method is available. The method is accomplished by adding a negative 50% of the reference voltage to the curve of the second capacitor
410
as shown in
FIG. 4A
, resulting in a new curve
30
′/
32
′ that has a point of inflection
31
′ intersecting with the time axis. The new charge/discharge curve is then integrated and inverted by the controller
700
, resulting in an integral curve shown in FIG.
4
B. The maximum integrated value, V
imax
, shown as point
41
in
FIG. 4B
, corresponds to the point of inflection
31
′ in FIG.
4
A. If the discharge of the second capacitor
410
occurs in the acceptable range shown by hatched area A in
FIG. 4A
, such as is the depicted by point
34
′, the discharge will appear in the acceptable range depicted by hatched area B in
FIG. 4B
as point
44
. A discharge that occurs too soon (which would appear along curve portion
32
′ in
FIG. 4A
) because of a spark gap that is too narrow appears on the integral curve portion
42
above the upper reference value V
ihi
. Similarly, a discharge that occurs too late, or not at all (which would appear along curve portion
39
′ in FIG.
4
A), because of a spark gap that is too wide will appear on the integral curve portion
49
below the lower reference value V
ilo
. In either case, the unacceptable discharge value would result in a correction signal being sent by the controller
700
. The most important benefit of integrating the voltage characteristic curve of the second capacitor
410
is a “magnified” look at the acceptable range resulting in a more accurate account of events.
The integration technique can be combined with the statistical analysis approach, both described above, to obtain an extraordinarily accurate method of determining and adjusting the spark gap
315
.
Of course, it should be understood that a wide range of changes and modifications could be made to the exemplary embodiments described above. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it be understood that it is the following claims, including all equivalents, which are intended to define the scope of this invention.
Claims
- 1. An electrode assembly, comprising:an insulator having a generally cylindrical body and a hollow interior having a threaded inner surface; an inner conductor disposed within said hollow interior and an outer conductor attached to the outer surface of said insulator; an inner electrode being connected to said inner conductor, an outer electrode cage being connected to said outer conductor, an outer electrode being connected to said outer electrode cage, said inner and outer electrodes being opposed and coaxially aligned, said electrodes having tips, the distance between said tips defining a spark gap; a first capacitor being connected to said inner and said outer conductors; an electrical meter connected to said capacitor; a device for adjusting the spark gap comprising a motor, a gearbox connected to said motor, and a threaded positioning element being engaged with said threaded inner surface of said insulator, said positioning element further being connected to said inner conductor; and, a controller being electrically connected to said motor, said capacitor, and said electrical meter, said controller comparing the discharge voltage of said capacitor to a predetermined reference value and issuing a correction signal to said motor when said discharge voltage differs from said predetermined reference value, whereby moving said tip of said inner electrode closer to or farther away from said tip of said outer electrode.
- 2. The electrode assembly of claim 1 further comprising:a second capacitor electrically connected to said first capacitor and said meter; said second capacitor being connected to said inner and outer conductors; an inductor electrically connected to said first and said second capacitors; whereby said controller compares the charge and discharge voltages of said second capacitor to predetermined reference values and issues a correction signal to said motor when said charge and discharges voltage differ from said predetermined reference values, whereby moving said tip of said inner electrode closer to or farther away from said tip of said outer electrode.
- 3. The electrode assembly according to claim 1 further comprising:a groove formed in the outer surface of said insulator capable of receiving said outer electrode cage; an inner locking ring slidably engaged with said electrode body, said inner locking ring for retaining said outer electrode cage within said groove; an outer locking ring slidably engaged with said electrode body and with said inner locking ring, said outer locking ring for retaining said inner locking ring.
- 4. The electrode assembly according to claim 3 wherein said inner conductor further comprises a threaded end and said inner electrode further comprises a threaded end, said threaded end of said inner electrode being engaged with said threaded end of said inner conductor.
- 5. A lithotripter electrode assembly, comprising:a insulator assembly comprising an insulator body, an inner conductor and an outer conductor; an electrode arrangement comprising an inner electrode having a tip and an outer electrode having a tip, said inner and outer electrodes being coaxially aligned and said tips being in relatively close physical proximity wherein the distance between said tips define a spark gap, said inner electrode being electrically connected to said inner conductor and said outer electrode being connected to said outer conductor; a charging system comprising at least one capacitor and a voltage source, said voltage source being electrically connected to said capacitor and said capacitor being electrically connected to said inner and outer conductors; means for measuring a discharge voltage of said capacitor, said measuring means electrically connected to said charging system; and, means for adjusting said spark gap, said adjusting means being connected to said electrode arrangement and further being electrically connected to said measuring means, said adjusting means being responsive to a discharge voltage of said capacitor.
- 6. The lithotripter electrode assembly according to claim 5 wherein said measuring means comprises a voltage meter.
- 7. The lithotripter electrode assembly according to claim 5 wherein said measuring means comprises an oscilloscope.
- 8. The lithotripter electrode assembly according to claim 5 wherein said adjusting means comprises:a motor; a gearbox connected to said motor; and, a positioning element being connected to said gearbox and said inner conductor.
- 9. The lithotripter electrode assembly according to claim 8 wherein said adjusting means further comprises:a controller being electrically connected to said motor, said capacitor, and said measuring means, said controller comparing the discharge voltage of said capacitor to a predetermined reference value and issuing a correction signal to said motor when said discharge voltage differs from said predetermined reference value, whereby moving said tip of said inner electrode closer to or farther away from said tip of said outer electrode.
- 10. The lithotripter electrode assembly according to claim 8 wherein said controller comprises a microprocessor.
- 11. A method of adjusting a spark gap of a lithotripter electrode assembly comprising the steps of:applying a voltage to a first capacitor being electrically connected to a first conductor and a second conductor whereby creating a spark across said spark gap; measuring the actual discharge curve of said spark created across said spark gap; comparing said actual discharge curve with a predetermined reference curve; and, adjusting said spark gap based on a difference between said actual discharge curve and said reference discharge curve.
- 12. The method according to claim 11 further comprising the steps of:applying the output voltage of said first capacitor to a second capacitor; measuring the actual charge curve of said second capacitor; comparing said actual charge curve of said second capacitor with a reference charge curve; adjusting said spark gap based on a difference between said actual charge and discharge curves and said reference charge and discharge curves.
- 13. The method according to claim 12 wherein said steps of comparing comprising said actual charge and discharge curves with said reference charge and discharge curves comprise:integrating said charge and discharge curve; and, inverting said charge and discharge curve; whereby determining whether said spark gap is adjusted properly by determining whether said discharge of said second capacitor occurs within an acceptable range.
- 14. The method according to claim 13 further comprising the step of offsetting the actual charge and discharge curve by a −50% of the reference voltage.
- 15. The method according to claim 12 wherein said step of adjusting said spark gap comprises:issuing a correction signal from a controller to widen or narrow said spark gap.
- 16. A method of adjusting a spark gap of a lithotripter electrode comprising the steps of:charging a first capacitor; discharging said first capacitor into a second capacitor whereby charging said second capacitor until said second capacitor discharges across said spark gap; measuring the actual charging and discharging voltages of said second capacitor; comparing said actual charging and discharging voltages of said second capacitor with reference charging and discharging voltages; and, adjusting said spark gap based on a difference between said actual charging and discharging voltages of said second capacitor and said reference charging and discharging voltages such that a subsequent discharge of said second capacitor occurs at the maximum load of said second capacitor.
- 17. The method according to claim 16 wherein said steps of comparing said actual charge and discharge voltages with said reference charge and discharge voltages comprise:integrating said charge and discharge voltages; and, inverting said charge and discharge voltages; whereby determining whether said spark gap is adjusted properly by determining whether said discharge of said second capacitor occurs within an acceptable range.
- 18. The method according to claim 17 further comprising the step of offsetting the actual charge and discharge voltages by a −50% of the reference voltage.
- 19. A method of adjusting a spark gap of a lithotripter electrode comprising the steps of:creating a spark across said spark gap by charging a capacitor until said capacitor discharges across said spark gap; measuring the actual discharging voltage of said capacitor; comparing said actual discharging voltage of said capacitor with a reference discharging voltage; and, adjusting said spark gap based on a difference between said actual discharging voltages of said capacitor and said reference discharging voltages.
- 20. The method according to claim 19 further comprising the steps of:discharging said capacitor to a second capacitor to create a spark across said spark gap; and, adjusting said spark gap based on a difference between said actual charging and discharging voltages of said second capacitor and said reference charging and discharging voltages.
- 21. The method according to claim 20 further comprising the steps of:recording a succession of charges and discharge voltage values; and, statistically analyzing said succession of values to determine a representative voltage value; and comparing said representative voltage value with a reference voltage value; and, adjusting said spark gap based on a difference between said representative voltage value with a reference voltage value.
- 22. The method according to claim 21 wherein said steps of comparing the representative voltage value with a reference voltage value comprises:integrating said representative voltage values; and, inverting said representative voltage values; whereby determining whether said spark gap is adjusted properly by determining whether said discharge of said second capacitor occurs within an acceptable range.
- 23. The method according to claim 22 further comprising the step of offsetting the actual representative voltage values by a −50% of the reference voltage.
- 24. A lithotripter electrode assembly, comprising:a insulator assembly comprising an insulator body and a pair of conductors; an electrode arrangement comprising a pair of electrodes wherein the distance between said each of pair of electrodes defines a spark gap, said pair of electrodes being electrically connected to said pair of conductors; a charging system comprising at least one capacitor and a voltage source, said voltage source being electrically connected to said capacitor and said capacitor being electrically connected to said pair of conductors; means for measuring a discharge voltage of said capacitor, said measuring means electrically connected to said charging system; and, means for adjusting said spark gap, said adjusting means being connected to said pair of electrodes and further being electrically connected to said measuring means, said adjusting means being responsive to a discharge voltage of said capacitor.
- 25. The electrode assembly according to claim 24 further comprising a second capacitor wherein said adjusting means is responsive to charge and discharge voltages of said second capacitor.
Priority Claims (1)
Number |
Date |
Country |
Kind |
8754829 |
Oct 1997 |
DE |
|
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