U.S. patent number 3,770,963 [Application Number 05/194,600] was granted by the patent office on 1973-11-06 for dental x-ray monitoring system.
This patent grant is currently assigned to Litton Medical Products, Inc.. Invention is credited to Robert Leino, Cornelius Keith Vandervelden.
United States Patent |
3,770,963 |
Vandervelden , et
al. |
November 6, 1973 |
DENTAL X-RAY MONITORING SYSTEM
Abstract
A control circuit for a dental x-ray head having a monitoring
system incorporated therein for apprising the x-ray machine
operator of various malfunctions that may occur within the x-ray
machine.
Inventors: |
Vandervelden; Cornelius Keith
(Kansas City, MO), Leino; Robert (Olathe, KS) |
Assignee: |
Litton Medical Products, Inc.
(Des Plaines, IA)
|
Family
ID: |
22718204 |
Appl.
No.: |
05/194,600 |
Filed: |
November 1, 1971 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
889505 |
Dec 31, 1969 |
|
|
|
|
Current U.S.
Class: |
378/118 |
Current CPC
Class: |
A61B
6/10 (20130101); H05G 1/54 (20130101); A61B
6/14 (20130101) |
Current International
Class: |
A61B
6/10 (20060101); A61B 6/14 (20060101); H05G
1/54 (20060101); H05G 1/00 (20060101); H05g
001/26 () |
Field of
Search: |
;250/99,95,93 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Archie R.
Assistant Examiner: Church; C. E.
Parent Case Text
This is a continuation of application Ser. No. 889,505, filed Dec.
31, 1969 now abandoned.
Claims
What is claimed is:
1. An x-ray system comprising
a. an x-ray tube exhibiting a characteristic emission current upon
application of filament and plate voltages thereto for generating
x-rays,
b. means connected to said tube for supplying said plate voltage
thereto,
c. means connected to said tube for supplying said filament voltage
thereto,
d. means for stabilizing said emission current,
e. emission current monitoring means for generating a signal X
indicative of said emission current,
f. inverting means receiving said signal X and generating a signal
X equal to the inverse of X,
g. plate voltage monitoring means for generating a signal P
indicative of plate voltage at said X-ray tube,
h. timer means for generating a signal T indicative of elaped time
within a preselectable exposure time period,
i. logic means for combining said signals X, X, P and T so as to
generate a signal M indicative of a signal equivalent to the
expression P.sup.. T.sup.. X + (P+T) X, and
j. control means for initiating and terminating the generation of
x-rays upon command from a human operator and for prohibiting the
generation of x-rays in the absence of said signals M and X which
are supplied to said control means only during proper operation of
said system.
Description
FIELD OF INVENTION
This invention relates to x-ray control circuits and more
particularly to dental x-ray control circuits having a monitoring
system incorporated therein.
DESCRIPTION OF THE PRIOR ART
Prior art x-ray machines incorporate control circuits which control
the various factors which affect the quality of an exposure.
Usually the operator is given an indication as to whether or not an
exposure has taken place. This indication may be in a form of a
light, a meter movement, or an audible signal. In the case of the
light or the audible signal, the indication can be erroneous
because although the light or the sound may be generated, no actual
exposure may have taken place. In the case of a meter movement, the
actual event of an exposure may be monitored by the operator but to
constantly observe the meter is usually not convenient because the
operator usually wants to watch the patient to ascertain whether or
not the patient has moved during the exposure. The above mentioned
seemingly positive indications of exposures have confused many
operators and in some cases dentists have thought that they have
taken exposures throughout the day only to find out upon attempting
to develop the film that none of the film was exposed.
Accordingly, it is an object of the present invention to provide a
novel control circuit which includes a monitoring system for
monitoring certain indicia of the control x-ray machine.
It is a further object of the present invention to provide a novel
control circuit which includes a monitoring system which shuts off
the control circuit if an improper exposure has occurred.
SUMMARY OF THE INVENTION
A control circuit having a monitoring system incorporated therein
for dental x-ray heads. The monitoring system comprises the x-ray
machine operator of various malfunctions that may occur within the
x-ray machine. Any malfunction that is monitored will immediately
shut down the control circuit so that no more improper exposures
will occur.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects, advantages and characteristic features of the
present invention will become readily apparent from the following
detailed description of the preferred embodiments of the invention
when considered in conjunction with the accompanying drawings in
which:
FIGS. 1a, 1b, 1c, and 1d represent an electrical schematic of a
control circuit for an x-ray head in accordance with the present
invention:
FIG. 2 is a truth table for the control circuit of FIG. 1 in
accordance with the present invention; and
FIG. 3 is a time sequence chart for the control circuit of FIG. 1
in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIGS. 1a, 1b, 1c, and 1d, there is shown an
electrical schematic of a control circuit for an x-ray head in
accordance with the present invention. Since various components,
and their respective arrangements thereof, within the control
circuit are well known in the electronics art, for the purpose of
simplification of explanation of the present invention, not every
component illustrated will be referred to specifically in this
specification. Furthermore, in order that one may more readily
understand the overall operation of the control circuit, the
electrical schematic has been separated into seven major blocks
which perform certain functions. The seven major blocks designated
by capital letters are as follows:
Block A defines a schematic diagram head of an x-ray head,
including an x-ray tube V1 and a high voltage transformer T5;
Block B defines that portion of the control circuit which
stabilizes the emitted current of the x-ray tube and therefore
stabilizes the intensity of the x-ray beam;
Block C defines a timing circuit which controls the duration of the
x-ray burst;
Block D defines a fixed timing circuit which introduces a delay
between the initiation of the x-ray exposure command and the
initiation of the actual x-ray exposure. Such a delay is necessary
in order to allow the filament of the x-ray tube V1 to reach
emission temperature;
Block E defines a stabilized power supply;
Block F defines a current for controlling the initiation of an
x-ray exposure; and
Block G defines that part of the control circuit which includes a
solid-state power contactor.
The remaining areas or parts of the control circuit either do not
perform major functions to justify separation from the other
components of the control circuit, or do not lend themselves to
being defined by blocks because they are illustrated in more than
one figure of the drawings. However, generally speaking, the upper
portion of FIG. 1a and the upper left portion of FIG. 1b includes
the components for placing the control circuit in operation and for
providing various voltages to the rest of the control circuit, and
the lower right portion of FIG. 1a and the right portion of FIG. 1c
includes the monitoring system of the control circuit.
Referring now specifically to monitoring system of this control
circuit, the monitoring element of the monitoring system is a relay
K2 which operates as follows: When the "on" button SW1 is
depressed, power is applied to a relay K1, via lines L1 and L2.
Power is then applied to a Transformer T1. The rectifying circuit,
comprised of CR1, CR2 and C1, generates a DC voltage which is
applied to relay K2 through the normally closed contacts of relays
K3 and K4. The rectified current is allowed to flow through the
coil of relay K2 by virtue of the fact that the coil is connected
to ground through a parallel set of contacts of the "on" button
SW1. The "on" button SW1 has to be kept depressed a fraction of a
second to allow the rectified voltage to build up and energize the
relay K2. Thus, the relay K2 will stay energized because one of its
contacts is connected to the "on" button SW1 through the "off"
button SW2. If it is desired to turn the control off, the "off"
button SW2 is depressed and the relay K2 will be released which in
turn releases the power relay K1.
The rest of the monitoring system is connected to the monitoring
element, relay K2, through the contacts of relays K3 and K4, which
are "true form C" contacts. It can be readily seen that if relays
K3 and K4 are not energized, that K2 is allowed to remain
energized. If both relays K3 and K4 are energized simultaneously,
the conduction path to K2 will switch from the normally closed
contacts of the relays K3 and K4 to the normally open contacts of
relays K3 and K4. Since relays K3 and K4 are of the dry-reed type
which have very short operating and release times, small
differences in the operator release times may be evened out by
means of circuit consisting of R42 and C6, which is in parallel to
K2. Thus, it is quite clear that as long as the relays K3 and K4
are energized or de-energized simultaneously, the relay K2 will
remain energized. However, if the synchronization of the signals
that are applied to the coils of the relays K3 and K4 is disturbed,
then no path will be present for applying power to K2. If this
condition exists, the relay K2 will release and the control circuit
will be turned off.
Such synchronization will not occur if there is an error in the
x-ray exposure and the monitoring system will sense such error in
the x-ray exposure so as to turn off the control circuit. The
turning off of the control circuit apprises the operator of a
malfunction within the x-ray machine in that he will not be able to
obtain any more x-ray exposure. The operator is normally apprized
of the fact that an x-ray exposure has been successfully obtained
through a light PL2 which would be mounted on the control panel. In
addition a light PL3 is provided on a remotely located exposure
button. If either one of these lights do not come on when the
exposure button is depressed, the operator is apprised of the fact
that a successful x-ray exposure has not occurred. An additional
indication of malfunctioning of the control circuit is provided
through a light PL1 located on the control panel.
To ensure proper synchronization of the control circuit, the coils
of relays K3 and K4 are connected to the filament circuit of the
x-ray tube V1 and to the output of the logic portion of the
monitoring circuit. The current which flows through K3 is the
current emitted by the filament of the x-ray tube V1 and therefore
the presence of this current is directly related to the presence of
an x-ray burst. The object of the logic portion of the monitoring
system is to apply to the coil of the relay K4 a signal which is
identical to the signal routed to the coil of the relay K3 in order
to ensure that K2 remains energized. The emitted current will
consist of approximate trapezoidal pulses because the x-ray tube V1
is of the self-rectifying type. The flat top of this wave shape is
a direct result of the constant current characteristic of the x-ray
tube V1 which is operated as a saturated diode. The duration of the
pulse is approximately one-half cycle of the line voltage and each
pulse is repeated a total number of times corresponding to the
setting of a variable resistor 49 in the exposure timer circuit of
block C. The fast acting contacts of the relay K3 will transfer
during the presence of the trapezoidal current pulse and will fall
back to the rest position in between two current pulses. Since the
contacts of the release K3 and K4 are connected as illustrated, it
can be seen that the monitoring signal which is applied to the coil
of the relay K4 should be identical in duration and amplitude to
the current signal sensed by the relay K3 to obtain
synchronization.
From this observation, a truth table can be readily constructed
which specifies the logic portion of the monitoring circuit. In
accordance with the objectives of the present invention, only
certain conditions are monitored, as follows: (1) the presence of
x-rays as evidenced by the emission of electron current in the
x-ray tube V1, such electron current signal will hereafter be
referred to as X; (2) the presence of a command from the timer
circuit to produce x-rays, such command signal will be hereafter
referred to as T; and (3) the presence of power being applied to
the primary of the high voltage transformer T5, such power will
hereafter be referred to as P.
Referring now to FIG. 2, there is shown a truth table in accordance
with the present invention. The truth table identifies eight
different conditions. In this truth table, the numeral one denotes
the presence of a signal and a zero denotes the absence of a
signal. Only conditions 1 and 8 represent normal conditions,
namely, normal exposure and standby, respectively. Condition 1
identifies the normal exposure condition wherein the emission of
x-rays is requested and takes place for the duration determined by
the timer circuit. The condition 8 is the standby condition wherein
the control circuit is turned on, but the emission of x-rays is
neither generated nor requested. Conditions 2 through 7 indicate
error conditions. The last column of the truth table illustrates
the required output of the monitoring logic circuit as specified by
the arrangement of the relays K3 and K4. It can be seen from the
truth table that the signal applied to the coil of the relay K4
should be identical to the signal applied to the coil of the relay
K3. Using the usual algebraic techniques, the following formula can
be extracted from the truth table: P.sup.. T.sup.. X + (P+T) X =
M.
The signal represented by X is obtained from the filament circuit
of the x-ray tube V1 and is applied to the coil of the relay K3 by
means of correcting resistors R72 and R76. The inverse of the
signal is called X and is obtained through an inverting amplifier
consisting of Q14 and R32. The signal which represents the
application of power to the primary of the high voltage transformer
T5 and which is called P, is obtained as follows: An isolation
transformer T3 is connected across the primary of the high-voltage
transformer T5. The secondary of T3 has one side connected to
ground and the other side to a circuit consisting of R39 and CR21.
The purpose of the latter circuit is to remove negative going
voltages so that at test point TP7 only positive going pulses will
be present and then only during the time that power is applied to
the primary of the high-voltage transformer T5. The turns ratio of
the transformer T3 is selected to obtain a signal of adequate
amplitude across the secondary even when the x-ray machine is
operated at its lowest permissible kilovoltage.
A third signal designated as T is obtained and consists of a
positive going clipped halves of a sine wave. It is derived as
follows: The output of the timer, which is a positive going square
wave of 15 volts that starts at the instant that the timer in Block
D has run out and which terminates when the timer in Block C runs
out, is present at a junction of R20 and R21. This signal is fed
into an "and" gate consisting of R22 and CR11. The other input to
the "and" gate applied to CR11 is a continuous train of half sine
waves which are in phase with the emitted x-ray beam. Q12 is an
amplifier and at test point TP3 the signal T can be observed. The
"or" gate consisting of CR13 and CR14 receives the signals called P
and T and therefore its output can be represented by the expression
P + T. The same signals P and T are combined with the signal X in
an "and" gate which is made up of components CR15, CR16 and R30.
The output of this "and" gate can be observed at test point TP5 and
is called P.sup.. T.sup.. X. The output of the "or" gate is
connected through R29 to Q14 which acts as an inhibitor. The signal
present at TP4 can therefore be represented by the expression (P+T)
X. This signal is then combined with the output of the "and" gate
which is observed on test point TP5 in an "or" gate consisting of
elements CR17 and CR18. This manipulation yields the final signal
represented by expression final P.sup.. T.sup.. X + (P+T) X. This
signal can be observed on test point TP6, and it is routed to
amplifier Q15 and then to the coil of K4.
Referring now to FIG. 3 there is shown a time sequence chart of
various events previously referred to that take place within the
control circuit illustrated. The time T.sub.0 represents the
control circuit being in the standby condition. The time T.sub.1
represents the time when the operator depresses the exposure button
PB. The time T.sub.2 represents the initiation of the exposure of
the x-ray burst. The period between time T.sub.1 and the time
T.sub.2 represents the filament warm up time of approximately one
second. The time T.sub.3 represents termination of the x-ray
exposure. The time T.sub.4 represents the time when the operator
releases the exposure button PB.
The top line represents the condition of the exposure button PB.
Two conditions identified are the released condition and the
depressed condition, as shown. The second line represents the
presence or absence of power to the filament of the x-ray tube. It
can be readily seen that as soon as the exposure button PB is
depressed, power is applied to the filament of the x-ray tube V1.
The third line represents the output of the timer in Block D, which
can be observed at the emitter of Q8. The fourth line represents
the output of the timer of Block C, which can be observed at the
junction of R20 and R21. The start of this signal is the start of
the output of the timer of Block D. The termination of this signal
occurs when the timer in the Block C has timed out the requested
exposure interval, or in other words, this signal represents the
firing of the circuit Q10 and Q11 which then shorts the output of
the Timer D. The output of the Timer C is applied to the "or" gate
of the monitoring circuit consisting of R22, CR11, and driver
transistor Q13, which through transformer T2 operates the power
contactor Q21. The power contactor Q21 will allow current to flow
to the primary of the high-voltage transformer T5 for as long as
Q13 is driven by the output of the Timer C. The fifth line
represents the application of power to the primary of the
high-voltage transformer T5. In the example shown in this time
sequence chart, an exposure time of five cycles has been chosen.
The sixth, seventh and eighth lines represent the signals X, P and
T, respectively. The ninth line represents the length of time that
the button light PL3 of the exposure button PB is on. It is seen
that this signal is identical to the duration of the application of
filament power to the x-ray tube V1.
Thus, although the present invention has been shown and described
with reference to particular embodiments, for example, an x-ray
tube within a dental x-ray head, nevertheless, various changes and
modifications obvious to a person skilled in the art to which the
invention pertains, for example, a solid state x-ray emitting
device within a dental x-ray head, are deemed to lie within the
spirit, scope and contemplation of the invention as set forth in
the appended claims.
* * * * *