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Патент USA US3043973

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July 10, 1962
'
E. B. GRAVES
3,043,957
PROTECTION DEVICE FOR ROTATING ANODE X-RAY TUBE
Filed Jan. 4, 1960
k L2
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37-"T/MER
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INVENTOR.
EDWARD B. GRAVES
United States Patent 0
1P
1C6
3,043,957
Patented July 10, 1962
1
2
3,043,957
are no other faults in the mechanism which would cause
improper or non-existent anode rotation. Other pro~
PROTECTION DEVICE FOR ROTATING ANODE
X-RAY TUBE
Edward B. Graves, South Euclid, Ohio, assignor to Picker
X-Ray Corporation, Waite Manufacturing Division,
Inc., Cleveland, Ohio, a corporation of Ohio
Filed Jan. 4, 1960, Ser. No. 270
16 Claims, (Cl. 250-103)
This invention pertains to X-ray devices and more spe
ci?cally to mechanisms which employ a rotating anode
type X-ray tube.
posals have often failed because if the condition testing
arrangement fails the exposure can nonetheless be made.
Still other proposals have failed because of complexity
and cost, while others have failed because they were sen
sitive to a limited range of anode speeds far less than the
actual'operative range. Some proposals, such as tempera
ture responsive mechanisms, are not su?iciently respon
10 sive to protect against a complete and sudden failure.
The present invention provides a simple, fool-proof
sensing arrangement which automatically initiates an ex
When an X-ray exposure is made, the anode of an
posure after an exposure button is pushed. This mecha
X-ray tube is ‘bombarded with a high energy beam of
nism can only automatically initiate the exposure if the
electrons emitted by the cathode of the tube. In the 15 anode and the novel condition responsive mechanism are
usual X-ray tube the cathode and anode are positioned
operating properly.
'
in a vacuum chamber and a high tension exposure cir~
cuit is connected to them. When an exposure is made
With this invention the windings of the X-ray tube in
duction ‘motor are energized. Subsequently, the winding
this circuit is closed and the bombarding of the anode
energizing circuit is broken and a condition responsive
occurs.
.
20 circuit is closed. If the anode is rotating the induction
This bombarding of the anode is usually focused on a
motor will operate as an induction generator. A back
relatively small target area in order that the X-rays
electromotive force is generated in the windings when
emitted as a result of the bombarding will be as concen
the anode is rotating. When the energizing circuit is
trated and focused as possible. This focused bombarding
broken the only current ?owing through the deenergized
causesthe target surface of the anode to become very 25 winding will be the current caused by the generated back
hot. Holding the anode temperature within permissible
The condition responsive circuit includes some
limits is the principal factor limiting the capacity of
sensing element which can be energized by the back
X-ray tubes.
This condition responsive element in turn 'will
One well established technique for increasing the ca
cause an exposure timer to start operating and an X~ray
pacity of the tube while maintaining the anode tempera; 30 exposure of a predetermined duration will be made.
ture within permissible limits is to provide a rotatable
In the preferred arrangement the condition sensing ele
anode which has an annular, usually frustoconical shaped
ment is one which is responsive to the back
gen~
target surface. To cause this anode rotation, a small in
erated in the winding by a minimum acceptable rotation
duction motor is incorporated in and forms a part of the
of the anode. Thus, if with a given X-ray tube the mini
X-ray tube. The tube anode, or target as it is often
mum
of sayacceptable
12 volts isspeed
generated
is 2,000
at rpm.
that speed,
and athe
back
condition
known, is mounted on the rotor of the induction motor
for rotation with the rotor.
responsive element will be one which requires at least 12
When the tube is in use the rotation is initiated before
volts to operate.
an exposure is made. The beam is then focused against
The usual rotating anode type X-ray tube has a pair of
a segment of the annular target surface. Since the tar 40 parallel connected windings. In the preferred arrange
get surface is rotating the segment of the surface which
ment the circuit energizing only one of those windings
is being bombarded is constantly changing as it moves
is broken. The other of the windings will maintain the
around the annulus so that the segment of the target being
anode’s speed at a satisfactory level substantially inde?
bombarded is constantly changing. This allows ample
nitely, and at least for a period which is far longer than
45
time for the target surface, to cool and permits extremely
any normal X-ray exposure period.
high energy and long duration exposures, relatively speak
Accordingly, one of the principal objects of the in
ing, as compared with other tubes.
vention is to provide a novel and improved mechanism
One long-standing problem which is inherent in these
rotating anode type X-ray tubes is that if the anode is,
in which an X~ray exposure can be taken with a rotat
concentration will cause that segment of the target sur
face to overheat and be burned or melted away. The
is automatically taken, but only if the anode is operating
ing anode tube only if the anode is rotating at a suitable
for some reason, either not rotating at an adequate speed 50 . speed.
or perhaps not rotating at all when an exposure is made,
Another object of the invention is to provide a novel
the tube in all probability will be destroyed. The tube
and improved mechanism in which, once the operator '
will be destroyed because the electron bombardment is
initiates the actuation of the mechanism, the rotating
‘concentrated on one segment of the target surface. . This
55 anode is brought to speed and thereafter an exposure
at a predetermined and acceptable minimum speed.
A further object of the invention is to provide a novel
shielded within a suitable housing to protect the operator
and improved mechanism in which an X-ray exposure
from exposure to X-rays, it is very di?icult to know
can be taken only if a rotating anode tube and a condi
whether or not the anode is actually rotating before an 60 tion responsive mechanism are both operating properly.
exposure is made.
Other objects and a fuller understanding of the in
A large number of proposals have been made in at
vention may be had by referring to the following descrip
tempts to provide some means of determining whether or
tion and claims, taken in conjunction with the accom
not an anode is actually rotating. All such proposals 65 panying ‘drawing, in which: have had serious shortcomings. One very common ar
FIGURE 1 is a wiring diagram showing the one form
rangement which is used for this purpose is a simple time
of the novel and improved anode protection.
delay arrangement. The theory is that given a suitable
The usual rotating anode type X-ray tube includes a
delay the anode will be up to a tolerable minimum speed.
small induction motor which causes the anode to ro
These time-delay arrangements presuppose a proper func 70 tate. The stator of this motorincludes windings repre
tioning of the circuits which excite the windings of the
sented by windings 10, '11 in the drawings.
problem is that since the X-ray tube must be carefully
X-ray tube induction motor, and presuppose that there
The winding 10 is connected through conductors 12,
3,043,957
13 to a source of electricity designated by L-l. A phase
shifting capacitor 14 is connected in series with the wind
ing 11 through conductor 15. The winding 11 and the
phase shifting capacitor 14 are connected to the con
ductors 1‘2, 13 to place them in parallel with the wind
ing 10 and connect them to the source of electricity L-l.
A squelch capacitor 17 is connected in parallel with the
Winding 11.
closes an exposure control switch 45. Closing of the
switch 45 connects the induction motor windings 10, 11
to the source of electricity L—1. If all of the elements
of the system are in proper operating condition, this will
cause the anode of the X-ray tube to begin to rotate and
come to full speed very quickly. The normal operating
speed of these rotating anodes is about 3,200 revolutions
A number of condition responsive circuits are suitable
Once the anode has reached operating speed, the cir
for the accomplishment of the’ present invention.
per minute.
In 10 cuit connecting the winding 11 to the source of electric
any such condition responsive circuit some means must
be provided to break the circuit energizing at least one
of the motor windings. A means responsive to back
generated in the winding is provided to initiate
the exposure when a generated
of a predetermined
magnitude exists. In the succeeding discussion one pre
potential may be broken and the combination of inertia
and the magnetism induced by the winding 10 will main
tain the speed of anode rotation at a very satisfactory
level. With the present system 2,000 rpm. is a speed
which is quite adequate to protect the anode. Preferably
the speed will not drop below this level, and in normal
operation of the device exposures will be made with the
speed of anode rotation of around 2,100 to 2,400 revo
ferred mode of accomplishing the invention is disclosed.
In light of the preceding discussion any skilled mechanic
will recognize that any number of alternate arrange
lutions per minute.
After a suf?cient time interval has elapsed, the solenoid
ments and sophistications may be utilized. At the same 20
19 is energized to actuate the switch 18 and connect the
time, the suitability of this embodiment particularly be
winding 11 to the recti?er 25. In the disclosed arrange
cause of its adaptibility to existing equipment will also
be recognized.
ment this time delay is provided automatically by the
The drawing shows a single pole, double throw switch
trigger tube 20 which ?res to energize the solenoid 19
18 which normally connects the phase shifting capacitor
after about one second delay.
14 and the conductor 15 to the winding 11. The switch
18 is controlled by a solenoid 19. The solenoid 1% is
breaks in the line, or other defects which permit
current to “sneak” from the winding 10 through the
winding 11 and thence back through the solenoid 30 to
the conductor 13, the switch 24 will be closed. When
the switch 18 connects the winding 11 to the recti?er 25,
the circuit energizing the winding 11 is broken. If the
anode is rotating a back
will be generated in the
winding 11. This back
will be in the order of
about 10 to 15 volts in the operating ranges under con
actuated after the windings 10, 11 have been energized
su?iciently long enough to permit the anode to be ro~
tating at the desired speed. Usually about one second is
an adequate time delay to permit the anode to reach its
speed of operation. The preferred and disclosed time
delay is a trigger tube 20 time delay which is in series
with the solenoid 19. The solenoid and-tube 19, 20 are
connected to the source of electricity L-l through con
ductors 21, 22 which are connected to the conductors
Assuming there are no
sideration. If this back E.M.F. is generated, the sensing
relay 35, or other suitable current sensing device, will
12, 13 respectively.
energize the timer. Energizing the timer will start an
exposure period and actuate the relay 40 to cause high
tension current to be imposed across the X-ray tube for
a predetermined and selectable time interval.
While the invention has been described with a great
deal of particularity and detail, it will be seen that it es
sentially comprises a means for connecting a winding of
a rotating anode type X-ray tube to a back
sensing
winding 11 through conductors 31, 312. The conductor 45 mechanism, which sensing mechanism actuates an X-ray
32 is connected at 33‘ to the conductor 13. The relay
tube exposure timer.
30 is what is known as a protector or “anti-sneaker.”
Although the invention has been described in its pre
If there is a break in the conductor 13 between the mo
ferred form with a certain degree of particularity, it is
tor windings 10, 11 and the connection 33, for example,
understood that the present disclosure of the preferred
When the solenoid 19 is energized the switch 18 con
nects the motor winding 11 to a normally closed switch
24. The normally closed switch 24 is in turn connected
to a recti?er 25 by a conductor 26. To complete the
recti?er circuit, the recti?er 25 is connected to the con
ductor 13 by a conductor 27.
A relay 30 is connected in parallel with the motor
the coil 30 will be energized by energy passing through 50 form has been made only by way of example and that
the windings 10, 11. This will hold the switch 24 open
to prevent the passage of line current through the con
dition sensing circuit. At the same time the impedance
numerous changes in the details of construction and the
combination and arrangement of parts may be resorted
to without departing from the spirit and the scope of the
of the relay 30 is high enough that back
invention as hereinafter claimed.
generated
in the winding 11 when the recti?er 25 is connected to 55
the winding 11 by the switch 18 will not cause the solenoid
30 to open the switch 24.
‘In addition to the winding 11, the recti?er 25 and the
switch 18, the condition sensing or condition responsive
circuit includes a sensing solenoid 35. The solenoid is
connected to the recti?er 2‘5 and actuated by the recti
?ed back
of the winding 11. The sensing solenoid
35 controls a normally open switch 36. The switch
36 is connected to an X-ray tube exposure control timer
37. The timer 37 in turn controls the high tension cir
cuit which energizes the X-ray tube shown schematically
What is claimed is:
1. In an X-ray device having an X-ray tube‘ including
a cathode and a rotatable anode and windings to induce
a magnetic ?eld to drive the ‘anode and a high tension
circuit connected to the tube, the combination of a
winding energizing circuit, exposure control means con
nected to the high tension circuit to maintain the circuit
normally open, a condition responsive means responsive
to a back
generated in the windings, other means
in said energizing circuit to open at least a part of the
energizing circuit and to connect the condition responsive
means to at least one of the windings when at least such
at 38.
part of the circuit is open, and said condition responsive
In the usual timer, a tube is ?red when the switch 36
means when so connected to the exposure control means
is closed. Firing of this tube energizes an exposure con
and to each such winding disconnected from the energiz
trol solenoid 40. The solenoid 40 closes a high tension 70 ing circuit causing the exposure control means to close
exposure switch 41 to connect high tension transformer
the high tension circuit when a back
is generated
42 to a high tension source L-2.
in one such disconnected winding.
Operation
2. The device of claim 1 in which the condition rc
When an operator wishes to take an X-ray exposure, he 75 sponsive means causes the exposure control means to close
3,043,957
5
6
.
the'high tension circuit only when predetermined mini
ing a secondary winding connected to the anode and to
'mum back
is present.
3(The device of claim 1 wherein the condition re
sponsive means is a relay.
4. The device of claim 1 wherein the other means
comprises a solenoid actuated switch and a time delay
means connected to the winding energizing circuit to
I
energize the solenoid after the windings have been ener
gized a predetermined length of time.
5. In combination a rotating anode X-ray tube, a high 10
the cathode, a plurality of parallel connected windings
for inducing a magnetic ?eld to cause said anode to ro~
tate, a winding energizing circuit including an exposure
control switch connected to said windings, a solenoid
actuated switch means in series with one of said wind
ings, a time-delay trigger tube series connected to the
switch means solenoid and connected in parallel with the
windings,‘ a recti?er in series with said switch means and
said one winding, said recti?er being energized when
said switch solenoid is energized and the anode is rotat
posure control timer operatively connected in the exposure
ing, a sensing solenoid connected to the recti?er, a timer,
circuit, said tube including ?rst and second windings
a sensing solenoid-controlled switch connected to the
for inducing a magnetic ?eld, a winding energizing cir
timer, and a high tension control switch connected to the
cuit connecting the windings in parallel to a source of 15 timer and other high tension circuit to close the high
electric energy, a condition sensing circuit, switch means
tension circuit and energize said transformer when the
in series with the ?rst winding and selectively connecting
sensing solenoid-controlled switch is closed to energize
the timer. >
the ?rst winding to the energizing circuit and to the
sensing circuit one at a time, and said sensing circuit
14. In combination, an X-ray tube including a cathode
including means responsive to a back
generated 20 and a rotatable anode, a high tension transformer includ
in said ?rst winding to actuate said timer when a back
ing a winding connected to the anode and to the cathode,
a plurality of windings for inducing a magnetic ?eld to
E.M.F. of a predetermined magnitude is generated in
such ?rst winding.
~
cause said anode to rotate, a winding energizing circuit
tension exposure circuit connected to the tube, an ex
including an exposure control switch connected to said
6. The device of claim 5 wherein said means respon
25 windings, a solenoid-actuatedtswitch means in series with
sive to the back
is a solenoid.
one of said windings, a time delay means series connected
7. The device of claim 5 wherein the switch means
to the switch means solenoid and connected to the ener
comprises a series connected solenoid and time delay
gizing circuit, a sensing solenoid connected to said switch
means connected in parallel with the windings.
8. The device of claim 7 wherein the time delay means
is a trigger tube.
means, said sensing solenoid being energized when said
'
9. The device of claim 5 wherein a phase shifting
capacitor is in series with said one winding.
10. In combination, an X-ray tube including a cathode
and a rotatable anode, a high tension transformer in
cluding a secondary winding connected to the anode and 35
switch solenoid is energized and the anode is rotating, a
timer, a sensing solenoid-controlled switch connected to
the timer, and a high tension control switch connected to
the timer and to the high tension circuit to close the
high tension circuit and energize said transformer when
the sensing solenoid-controlled switch is closed to ener
to the cathode, ?rst and second parallel connected wind
gize the timer.
ings for inducing a magnetic ?eld to cause said anode
to rotate, a winding energizing circuit including an ex
posure control switch connected to said windings, a
15. In combination, an X-ray tube including a cathode
and a rotatable anode, a high tension transformer in
cluding a winding connected to the anode and to the
'
series with one of said windings, a time delay trigger
nected in parallel with the windings, a recti?er in series
with said single pole double throw switch and said one
inducing a magnetic ?eld to cause said anode to rotate,
a winding energizing circuit including an exposure con_
trol switch connected to said windings, switch means in
series with one of said windings for disconnecting said
solenoid is energized and the anode is rotating, a sensing
means is actuated, a time delay means connected to the
single pole double throw solenoid actuated switch in 40 cathode, a plurality of parallel connected windings for
tube series connected to the switch solenoid and con~
winding, said recti?er being energized when said switch 45 one winding from said energizing circuit when the switch
solenoid connected to the recti?er, an exposure control
timer, a sensing solenoid control switch connected to
the timer, and a high tension control switch connected
to the timer to close the high tension circuit and ener 50
gize said transformer when the sensing solenoid control
switch is closed to energize the timer.
11. In combination, an X-ray tube of the rotating
anode type, said tube including a plurality of windings,
a winding energizing circuit parallel connecting the wind 55
ings, a high tension exposure circuit connected to the
X-ray tube and including a normally open switch means,
a sensing circuit including switch control means to close
the normally open switch means when the sensing cir
cuit is energized, and control means connected to said
switch means and connected to said winding energizing
circuit for actuating the switch means a predetermined
time interval after the exposure control switch has been
closed, a sensing means connected to said one winding
when said switch means is actuated, said sensing means
being energized by the induced current flowing in said
one Winding when the anode is rotating, a high tension
control means connected to the high tension control cir
cuit to close the high tension circuit and energize said
transformer, said high tension control means being ac
tuatable by the sensing means when the induced current
exceeds a predetermined minimum value and the sensing
means is connected to said one winding.
16. In combination, an X-ray tube including a cathode
and a rotatable anode, a high tension transformer includ
ing a winding connected to the anode and to the ‘cathode,
a plurality of parallel connected windings for inducing a
magnetic ?eld to cause said anode to rotate, a Winding
65 energizing circuit including an exposure control switch
duced current ?owing in the one winding.
connected to said windings, switch means in series with
12. The device of claim 11 wherein the control means
one of said windings for disconnecting said one winding
includes a time-delay means energized by the energizing
from said energizing circuit when the switch means is
circuit and a selection switch actuated by the time-delay
actuated, a time delay means connected to the switch
means a predetermined time interval after the energizing 70 means and connected to said winding energizing circuit for
circuit has been closed, and wherein the selection switch
actuating the switch means a predetermined time interval
energizing circuit and said sensing circuit‘ to selectively
disconnect one of the windings from the energizing cir
cuit and connect said one winding to the sensing circuit
and thereby energize the sensing circuit only with in
disconnects said one winding and connects said one wind
ing to the sensing circuit after such interval.
13. In combination, an X-ray tube including a cathode
and a rotatable anode, a high tension transformer includ
after the exposure control switch has been closed, a sens
ing means connected to said one winding when said switch
means is actuated, said sensing means being energized by
75 the induced current ?owing in said one ‘winding when
3,043,957
I,
i
the anode is rotating, a timer, a sensing means controlled
switch connected to the timer and actuatable by the sens
ing means when the induced current exceeds a predeter
mined minimum value and the sensing means is con
nected to the one winding, and a high tension control
switch connected to the timer and to the high tension 5
control circuit to close the high tension circuit and ener
gize said transformer when the sensing means controlled
switch is closed to energize the timer.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,185,826
2,332,044
Atlee _________________ __ Jan. 2, ‘1940
Bell __________________ .._ Oct. 19, 1943
2,883,554
Reed et a1 _____________ __ Apr. 21, 1959
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