Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to a dental
x-ray machine for taking a panoramic or full mouth x-ray of the
patient's teeth. More specifically, the present invention
relates to a dental x-ray ~or taking full mouth x-rays by
rotating the x-ray source and x-ray film about the head of the
patient through a path of travel which closely approximates the
shape of the dental arch.
Various techniques and apparatus for taking a full mouth
x-ray are well known in the art. When taking a full mouth x-ray,
it is important that the x-ray source and film be moved about
the head of the patient through a path of travel which closely `~--
parallels the dental arch with the depth of focus between the
x-ray source and film following along a path on the dental arch.
In this way, only the particular tooth being radiographed remains
in focus. The difficulty is that the dental arch is not easily
approximated so that systems of the prior art only generally
followed the dental arch by rotation around a aouble or triple
center of rotation or utilized an ellipsograph-type drive to move
the x-ray source and film around the outline of an ellipse. -
Other systems required that the patient be moved laterally in
order to change the center of rotation or stepped the arive
through several centers of rotation in an attempt to approximate
the shape of the dental arch. ~ -
The size of the dental arch varies from patient to patient
and with the exception of the ellipsograph type drive~ the
apparatus of the prior art could only adjust the pattern size
in very coarse steps requiring considerable effort on the part
of the operator.
Prior art panoramic x-ray machines also located the drive
mechanism as well as the high voltage power supply for the
x-ray source above the head of the patient. This re~uired `
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relatively massive support columns and in some cases the
structure had to be wall mounted to prevent toppling of
the top heavy apparatus. Wall mounting is also necessary
in order to dampen any vibration produced by the drive
as such vibrations will reduce the quality of the x-ray
picture. Vibrations are caused, in particular, by drives ~,
of the prior art in which the mechanism is stepped from
one center of rotation to another.
The present invention relates to dental X-ray-
apparatus of the type for taking a full mouth X-ray by
orbiting an X-ray source and X-ray film holder about the
head of a patient along an orbital path which follows the
shape of the patient's dental arch, comprising a) a fixed
base supporting a patient chair; b) a platform movable
with respect to the base and chair through a closed path ~~
of travel in an X-Y plane beneath the chair; c) a column
; upstanding from the platform supporting the X-ray source
and X-ray film holder, the column being rotatable about
a vertical axis of rotation while being transported through
j the closed path of travel by the platform such that the
X-ray source and X-ray film holder are orbited about the
; head of a patient through an orbital path which parallels the
shape of the dental arch; and d) X-Y drive means carried by -
the platform and cooperating with the base for moving the
platform with respect to the base through the closed path
of travel.
Such apparatus overcomes the drawbacks of the
prior art by locating and X-Y drive mechanism and the high
voltage power supply in the base of the apparatus beneath
the seat of the patient's chair thus avoiding any massive
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overhead structure and the need for wall mounting. The
X-Y drive mechanism is controlled by a cam which produces
a smooth motion and this motion, when coupled with rota-
tion of the X-ray source and fllm holder about the head
of the patient, produces a net movement which allows the
focal plane between the X-ray source and film to follow ~
along the shape of the dental arch. The cam drive also ~ -
allows the size of the pattern to be quickly and easily
changed in an infinite number of steps over the entire
adjustment range.
Another feature of a particular embodiment is
an automatic apex adjustment which displaces the X-ray
axis of rotation towards or away from a fixed reference
point whenever the pattern size is respectively decreased
or increased. This aliows positioning both the adult and -
child patient at the same fixed reference point correspond-
ing to the front of the patient's mouth so that the X-ray
source and film holder will be properly oriented to the ~
patient regardless of his or her size. - -
The advantages and characterizing feature of ~ i
the present invention will become more apparent upon
consideration of the following detailed description
thereof when taken in connection with the accompanying
drawings depicting the same.
,
Figure 1 is a side elevation view showing
the dental X-ray,apparatus of the present in-
vention;
Figure 2 is a front elevation view of the
apparatus base, partly away and in section, showing X-Y
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drive on an enlarged scale;
Figure 3 is a plan view of the X-Y drive with
portions removed for clarity;
Figure 4 is an elevation view on an enlarged
scale of a portion of the Y-reaction arm of the drive;
Figure 5 is a view similar to Figure 3 with
still further portions removed for clarit~ to show the
X-reaction arm and apex adjustment mechanism;
Figure 6 is an elevation view on an enlarged
scale of an apex compensating mechanism associated with ;~
the X-reaction arm; and -.
Figure 7 is a plot showing the X-Y drive path
of travel and the net movement generated by the apparatus .
when taking an X-ray of a large and a small dental arch. ~
Referring to the drawings, Figure 1 shows the ~` .
X-ray appa.ratus of the present invention generally indi-
cated at 10. .
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The apparatus includes a supporting base 12, a patient chair
14 carried by the base, and a column 16 upstanding from the
base and supported for rotation about a vertical axis passing
generally through the seat of the patient chair. Column 16
is generally L-shaped wherein the horizontally deposed leg
17 passes beneath the seat of the chair. At the top of column
16 is an x-ray source 18 and an x-ray film cassette 20. The
cassette is supported on a curved outwardly extending horizontal
arm 22, so that the patient to be x-rayed can be positioned
between the x-ray source and the film cassette. The upright
structure indicated at 24 at the front of the dental chair
and the chin and forehead rests 26, 28 respectively are used
for properly positioning the patient. It should be appreciated,
that the chin and forehead rests define a fixed reference point
for properly positioning the head of the patient for the x-ray
procedure. In order to bring patients of different sizes to
this reference point, chair 14 can be raised or lowered and -
the backrest 30 moved on ways 32 front-to-back of the chair.
A transformer 13 and other electrical components for
activating the x-ray source are located within base 12 at any
convenient location, preferably at a rear portion thereof. -
A flexible electrical cable 15 extends from the transformer
and passes up through column 16 (including leg 17) for connecting
the power supply to the x-ray source. -
Disposed within base 12 is the means for rotating the
column about its vertical axis and for moving the axis of
rotation through a closed path of travel in the X-Y plane.
As shown in Figure 2, base 12 is generally U-shaped in cross-
section having a horizontal base leg 34 and upstanding sides
36 a and b. The base or horizontal leg 34 is adapted to rest
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on a floor surface and is provided with a pair of spaced parallel
ways 3~ which are oxiented along the X axis of the base, that
is, front-to-back. Slidably carried on these ways is a carriage
40.
Carriage 40 is also U-shaped in cross-section having
a base 42 and upstanding front and rear wall members 44, only
the rear one of which is shown in Figure 2. The carriage
in turn, carries adjacent the upper end of each wall 44 a pair
of parallel ways 46. Ways 46 are oriented normal to ways 38
and are aligned generally along the Y-axis of base 12 or side-
to-side. Slidably carried on ways 46 is a platform 48. Due -
to the orientation of ways 38 and 46, it should be apparent
that platform 48 can be moved along both the X and Y axis of
base 12.
Suspended from platform 48 are a plurality of columns -
50 which in turn support a plate 52 in spaced relationship
from platform 48. Disposed between the platform and the plate
and carried in part by the plate are the various mechanisms
for driving the platform through a closed path of travel in
the X-Y plane.
As shown in Figure 2, an upright shaft 54 is supported
by and is journaled to platform 48 and plate 52 by means of
bearings 51, 53 respectively. With this arrangement, the shaft
is ~ree to rotate about its vertical axis while the axis is -
being transported through a closed path of travel in the X-Y
plane~ It should be appreciated that the horizontal leg 17
of column 16 is fixed at one end to the portion 56 of the shaft
located above platform 48. The portion 58 of the shaft located
between platform 4~ and plate 52 is fixed to a cam member 60.
The cam is generally disc-shaped having endless grooves
62 and 64 cut into the top and bottom surfaces respectively
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of the disc, These grooves comprise the cam surfaces for
programming the motions of the platform as further set out
herein below.
A drive motor 66 fixed to plate 52 rotates the cam and
therefore, shaft 54 by means of a drive belt 68 which engages
around the periphery of the cam.
In order to translate the movement of cam surfaces 62,
64 into motion of platform 48 through a closed path of travel
in the X-Y plane, a cam follower is associated with each of --
the cam grooves. In this respect, cam groove 62 and its
associated cam follower cooperate to move platform 48 through
the Y component of travel (side-to-side) whereas cam groove
64 and its associated cam follower cooperate to mo~e platform
48 through the X component of travel lfront-to-back). The
net result is movement of platform 48 through a closed path
of travel in the X-Y plane.
~ Referring to Figures 2, 3 and 4 the cam follower associated -
with groove 62 includes a horizontal pick-off arm 70, which
is journaled at one end 72 to platform 48 by means of a vertical
shaft 74 extending between the platform and plate 52 (Figure ~ ~
2). Fixed to pick-off arm 70 at a given point along the arm -
is a cam follower 76, best seen in Figure 4, which rides in
cam groove 62. The distance between cam follower 76 and shaft
74 is a fixed dimension and as the cam rotates under the fixed
cam follower, the pick-off arm rocks about its journaled end
72 depending upon the radial distance of the cam groove from
shaft 54.
As shown in Figures 3 and 4, pick-off arm 70 is provided
with a lead screw 78 which drives a nut 80 along the arm to
increase or decrease respectively the linear distance of the
nut from shaft 74. Upstanding from nut 80 is a pin 82 which
is in turn, journaled to one end of a ri~id reaction arm 84,
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The other end of reaction arm ~ is slidably mounted on a way
86 carried at the top of upstanding base side 36a, way 86 being
alligned generally parallel to ways 38 (Figures 2 and 3).
With this arrangement, reaction arm 8~ is free to move
along the x-axis of the base, but is fixed against movement
in the Y direction. Thus, as cam disc 60 is rotated and the
radial distance of cam groove 62 changes with respect to shaft
54, the reaction arm will force platform 48 to move to the
left or the right as viewed in Figures 2 and 3. For example,
as the radial distance of cam groove 62 from shaft 54 increases,
the entire mechanism supported by platform 48 will shift to ~ -
the left as viewed in Figure 3 and conversely, will shift to
the right as viewed in Figure 3 when the radial distance
decreases. Moreover, as described more fully hereinbelow the
effect of the throw of the cam groove 62 can be increased or
decreased proportionally by moving nut 80 respectively away ~-
from or towards, shaft 74 in order to change the overall size
of platform movement in the Y direction.
A somewhat similar arrangement is provided for translating
the rotational movement of cam groove 64 into movement of
platform 48 along the X axis of base 12. In this respect,
Figure 5 is a plan view of the X-Y mechanism similar to Figure
3 only with some parts removed for clarity, such as pick-off
arm 70, reaction arm 84 and portions of cam disc 60.
Figure 5 shows a second, generally L-shaped pick-off
arm 88 having legs 90 and 92. At one end of the pick-off arm
(leg 90) i9 a cam follower 94 which extends up into cam groove
64 cut into the bottom surface of cam disc 60. Pick-off arm ~ -
88 is also journaled intermediate its ends to vertical shaft -
74 so that the distance from the shaft to cam follower 94 is
a fixed distance. The other leg 92 of the L-shaped pick-off
arm carries a lead screw 96 which in turn drives a nut 98
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(Figure 3). The ad;ustment of this nut along leg ~2 accomplishes
a result similar to the adjustment of nut 80 along pick-off
arm 70. In other words, such movement will either scale up
or down the effect of a throw o cam groove 64 depending upon
whether the nut is moved respectively away from or towards
shaft 74.
Extending horizontally from upstanding side 36b of the
base is a fixed member 100 only a portion of which is shown
in Figure 5. Since this member is fixed to side 36b, it ~
represents a ground station. A way 102 is carried on member
100, the way being oriented generally parallel to ways 46 and -
normal to ways 38 (Figures 2 and 3). . Slidably carried on
way 102 is an apex adjustment means generally indicated at -~
104. I~hile this means will be described more fully herein - -
below, it i5 sufficient for the present merely to say that ~ ;
the apex adjustment means 104 is also pinned to nut 98 so that
it is similar in one aspect to reaction arm 84. That is, means
104 is free to slide with the X-Y drive mechanism in either
direction along the Y axis of base 12, but it is fixed by member
100 against movement in the X direction. Thus, any variation
in the radial distance of cam groove 64 from shaft 54 is
translated into movement of platorm 48 in the ~ direction.
For example, as the radial distance decreases, the L-shaped
pick-off arm 88 will rock clockwise about shaft 74 causing
the platform 48 to shift toward the top o the Figure as view
in Figures 3 and 5 which is towards the back of the apparatus,
Conversely, any incxease in the radial distance of the cam
groove 64 from shaft 54 will cause the L-shaped arm to rock
counter-clockwise about shaft 74 causing the platform to shift
direction towards the bottom of the Figure as view Figures
3 and 5 which is toward the front of the apparatus.
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Thus, the mechanism described herein above cooperates
in response to rotation of cam disc 60 to move platform 48
and therefore, the axis of rotation of column 16 in a closed
path of travel in the X-Y plane. As column 16 is connected
to shaft 54, rotation of cam 60 will likewise, rotate the
column. For example, the path of travel generated by the X-Y
drive is shown in Figure 7 at 130~ Only one half the curve
is shown and it should be understood that the missing portion
is a mirror image of that shown. It should be appreciated
that reference 130 represents the path of travel of shaft 54
and therefore, the axis of rotation of column 16. The curve ~ -
132 in heavy solid line represents a locus of points within
the depth of focus and includes both the mandibular joints
and the dental arch. Points 1-8 represent various positions
of the x-ray film during the x-ray procedure and are along
a path generally parallel to the dental arch. The position
of the x-ray source, while not shown is understood to be on
the far side of the axis of rotation from points 1-8. From -
Figure 7, it should be apparent that the rotational movement
o~ the column, when associated with the movement in the X-Y
plane of platform 48 from which the column upstands, produces -~
a ne* movement of the x-ray source 18 and film cassette 20
along a path of travel which parallels the dental arch. As
shown by heavy solid line 132 in Figure 7, the x-ray is taken - -
starting at the left mantibular joint Li. It then moves inward
to x-ray the last molar L4 on the left side and then along
the dental arch to the last molar R4 on the right side of the
mouth and then outward to x-ray the right mandibular joint Rl.
As previously stated, the size of the pattern traveled
by the platform can be changed by moving the points of the
pick-o~fs defined by nuts 80 and 98. This is accomplished
by the simultaneous rotation of lead screws 78 and 96 to move ~`
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the nuts toward or away from shaft 74. For this purpose, a
second drive motor 106 is mounted on plate 52 ~Figures 3 and ~ -
5). When actuated, this motor drives both lead screws through
a system of bevel gears 108. Aceuation of the motor can be
accomplished by any suitable means (not shown) such as a hand
controller. It should be appreciated that such an arrangement
allows an infinite adjustment of the pattern size within the
full limits of the adjustment range.
As the pattern size is adjusted, it is important that
a common reference point be maintained for all pattern sizes. : ~;
Preferably, this common point is located at the front of the
dental arch, as defined, for example, by the chin and head rests
26, 28 respectfully, at the front of the dental chair which are
used for properly positioning the patient. For example, Figure 7
- shows at 130 a path of travel as may be generated by the mech-
anism for making a full mouth dental x-ray of the dental arch
of an adult. Reference 130a line shows a smaller, symmetrical,
pattern of the path generated for making an x-ray of a younger -
person whose dental arch is included in the light solid line
curve shown at 132A. The point indicated at A is common to
both patterns and is located at the front or apex of the -
dèntal arch.
Thus, when the size of the pattern is changed, it is
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necessary to provide an ad;ustment which maintains the position
of point A. This i5 accomplished by an apex ad~uster which
shifts the X-Y path of travel towards point A when a child i9 in
the chair and away from point A when an adult i~l ln the chair.
The apex ad;uster generally indicated at 104 can be seen
in plan view in Figures 3 and 5, and in elevation view in
Figures 2 and 6. As described hereinabove, there is a way
I02 mounted on member 100, which in turn is attached to the
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ground of the apparatus. Also as previous stated, way 102 i~
oriented parallel to ways 46 and normal to way 38 (Figure 3).
Slidably mounted on way 102 is a block 110. The ends 112 of
the block (Figure 6) are mitered and slidably fit into a pair
of horizontal side supports 114. Supports 114 extend in canti-
lever fashion from a mounting bracket 116 which depends from
platform 48 (Figures 2 and 3). With the arrangement described
thus far, it should be appreciated that block 110 is free to
sllde with platform 48 in the Y direction of the chair, but
that the block, being on way 10~, is fixed from sliding in the
X direction. However, due to the sliding relationship between
block 110 and side supports 114, the supports and platform 48
can slide with respect to the block in the X direction.
To accomplish the apex ad~ustment, which requires move-
ment in the X direction or front-to-back, Figures S and 6 show
that block llO contains a diagonal cam groove 118 which slid-
ably retains a follower 120. The follower depends from nut 98
and is therefore tied, via leg 92 and shaft 74, to platform 48 -
with the screw permitting an adjustment of the nut wlth respect
to the platform. Cam groove 118 is oriented generally on the
diagonal of block 110 to accomplish the apex ad~ustment as set
out hereinbelow.
As previously stated, rotating screw 96 to move nut 98
with respect to platform 48 to the left or the right as viewed
in the Figures, will respectively increase or decrease the size
of the x component at the pattern. Movement of the nut will in
turn drive follower 120 agalnst one side or the other of inclined
slot 118. The pressure of follower 120 against the side of
slot 118 cannot be relieved by a corresponding movement of
platform 48 ln the Y direction as move~ent in the Y direction is
prevented by reaction arm a4.. Consequently, such pressure is
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relieved by follower 120 riding up or down the inclined slot as
viewed in Figures 3 and 5. As follower 120 i9 tied to plat-
form 48, movement of the Eollower in the X direction produces a
like movement of platform 48, wherein the platform, bracket 116
and side supports 114 slide over block 1lO in the X direction.
By way of example, if nut 98 is moved to the left,-as
viewed in the Figures, to increase the size of the pattern,
follower 120 will be forced up the inclined slot 118 ~igures --
3 and 5) moving platform 48 towards the back of the apparatus
and away from the reference defined by chin and head rests 26,
28 respectfully. If the nut moves in the opposite direction
to decrease the pattern size, follower 120 will be forced down
the inclined slot moving platform 48 towards the reference
point defined by the chin and headrests. Such movement towards
and away from the chin and headrests maintains the key position
of the apex of the pattern at point A (Figure 7~ as the pattern
size is changed.
Thus, it should be appreciated that the present invention
accomplishes its present objects in providing a dental x-ray
apparatus for taking full mouth x-rays which is a self-contained ;
- unit requiring no installation or wall support. The apparatus
has-the capability of making an lnfinite ad~ustment af the size
of the-pattern followed by the x-ray soùrce and the film holder
about the head of the patient. Such change in the pattern size
is accomplished quickly and easily while maintaining a common
reference point with respect to all of the pattern slzes. The
ma~ority of the weight of the apparatus, made up by the trans-
former and other electrical components and the X-Y drive mechan-
ism, is located in the base of the apparatus, so the apparatus
can be made free standing and there is no need to wall supports
for mounting the apparatus.
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Since the present invention concerns primarily the
general arrangement of the x-ray apparatus together with X-Y
drive and apex adjustment as described herein, no mention is made
of other features well-known in the art which are essential to
the operation of a panorama dental x-ray machine of the type
described. For example, it is well-known that as column 16 is
rotated about a patient, means must be provided to accomplish
an independent rotation of x-ray film cassette 20 in order to
achieve proper exposure of the x-ray film. The rotation must be
in a particular time sequence with the movement of arm 16, but
as such a mechanism forms no part of the present invention, -
none has been described herein and the apparatus to accomplish
this has been omitted from the drawing for purposes of
simplification.
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