Title:
APPARATUS FOR TAKING A CONTINUOUS X-RAY PICTURE OF THE DENTAL ARCH
United States Patent 3806732


Abstract:
An apparatus for taking a continuous X-ray picture of the dental arch, wherein the X-ray tube and the film are moved together in such a manner that the line connecting them crosses an ellipse approximating the dental arch of a patient, always making a right angle with a line tangent to the ellipse, without disturbing the relative position of the X-ray tube and the film. The shape of the ellipse can be changed in accordance with the shape of the dental arch of each individual patient to be photographed.



Inventors:
Kataoka, Kenzo (Kyoto, JA)
Hozumi, Kazuo (Kyoto, JA)
Application Number:
05/236119
Publication Date:
04/23/1974
Filing Date:
03/20/1972
Assignee:
KK MONITA SEISAKUSHO,JA
Primary Class:
Other Classes:
378/168
International Classes:
A61B6/14; (IPC1-7): G03B41/16
Field of Search:
250/50,61.5,65R,7
View Patent Images:
US Patent References:
3673408COMBINATION RADIOGRAPHIC APPARATUS1972-06-27Moss
3636349CONTINUOUS ORBIT PANOGRAPHIC X-RAY1972-01-18Faude et al.



Primary Examiner:
Lindquist, William F.
Attorney, Agent or Firm:
Christensen, O'Connor, Garrison & Havelka
Parent Case Data:


RELATED APPLICATION

This application is a continuation-in-part of our copending application Ser. No. 96,890, filed Dec. 10, 1970 under the title APPARATUS FOR TAKING A CONTINUOUS X-RAY PICTURE OF A DENTAL ARCH, and now abandoned.
Claims:
What we claim is

1. An apparatus for taking a continuous X-ray picture of the dental arch, comprising: a base; first and second pins fixed on said base at a distance apart from each other; an elongated support member for supporting an X-ray tube and an X-ray film at the opposite ends thereof respectively, and having a first slot formed intermediate the length thereof; a third pin fixed on said support member; a first arm pivoted to said support member by said third pin and having at one end thereof a second slot in which said first pin slidably engages; a second arm having one end pivoted to the opposite end of said first arm; a third slot formed in said base in coincidence with a straight line connecting said first and second pins; a fourth pin fixed on the opposite end of said second arm and engaging in both said first and third slots; sprockets on the first, second, and third pins; a loop member endlessly passing about the sprockets and adapted to be driven so as to drive said third pin along the locus of an ellipse; said dental arch being operatively disposed intermediate said X-ray tube and film with the major axis of an ellipse approximating said dental arch coinciding with the straight line connecting said first and second pins; and means whereby at least one of said first and second pins is displaceable relative to the other along the line connecting said first and second pins, to vary the eccentricity of the ellipse travelled by the third pin.

2. The apparatus of claim 1, further comprising means whereby the displaced position of the one pin is determined by the distance between a pair of levers adapted to engage the jaw of the dental patient therebetween.

3. In apparatus for recording a continuous X-ray picture of the dental arch, a fixed reference, a relatively rotatable drive member which is cam connected with the reference and equipped with an X-ray source and an X-ray film holder on opposite sides of the cam connection therebetween, a relatively articulated linkage cam connected with the reference and with the drive member at the cam connection between the drive member and the reference, means forming a pivotal connection between the linkage and the drive member, drive means operable to cause the pivotal connection between the linkage and the drive member to move through an elliptical path, and thereby cause the source and the holder to trace coaxial elliptical paths, and means for varying the eccentricity of the elliptical paths of the source and the holder.

4. The apparatus according to claim 3 wherein the drive means includes a power unit and a system of rotary members on the reference and the pivotal connection between the linkage and the drive member, interconnected with one another and with the power unit to be driven in unison by the unit; and wherein one of the rotary members is selectively shiftable in relation to the reference to vary the eccentricity of the elliptical path of the pivotal connection between the linkage and the drive member.

5. The apparatus according to claim 4 further comprising a calipers for determining a variable distance, and means operable to shift the one rotary member in relation to the reference, commensurate with the variation in said distance determined by the calipers.

6. The apparatus according to claim 3 wherein the drive means includes a power unit on the drive member, a rotary member on the pivotal connection between the linkage and the drive member, driven by the power unit, a pair of spaced rotary members on the reference, one of which is coaxial with the cam connection between the linkage and the reference, and a rotary connection between the rotary member on the pivotal connection between the linkage and the drive member and each of the rotary members on the reference, whereby the rotary member on the pivotal connection between the linkage and the drive member is caused to trace an elliptical path as it is driven by the power unit, the other rotary member on the reference being selectively shiftable in relation to the reference to vary the eccentricity of the elliptical path of the rotary member on the pivotal connection between the linkage and the drive member.

7. The apparatus according to claim 6 wherein the rotary connection takes the form of a flexible band interengaged about the respective rotary members on the reference and the pivotal connection between the linkage and the drive member.

8. The apparatus according to claim 7 wherein the reference has an arcuate guide thereon, and there are yieldable biasing means interposed between the guide and the drive member to maintain tension in the band.

9. The apparatus according to claim 3 wherein the cam connections take the form of pin and slot connections.

10. In combination, a fixed reference, a relatively rotatable drive member which is cam connected with the reference and equipped with an X-ray source and an X-ray film holder on opposite sides of the cam connection therebetween, a relatively articulated linkage cam connected with the reference and with the drive member at the cam connection between the drive member and the reference, means forming a pivotal connection between the linkage and the drive member, drive means operable to cause the pivotal connection between the linkage and the drive member to move through an elliptical path, and thereby cause the source and the holder to trace coaxial elliptical paths, and means for varying the eccentricity of the elliptical paths of the source and the holder.

Description:
BACKGROUND OF THE INVENTION INCLUDING CERTAIN OBJECTS THEREOF

This invention relates to improvements in an apparatus for taking X-ray pictures of the dental arch of a human being, wherein the X-ray tube and the film are moved along the dental arch of the patient so as to take necessary X-ray pictures thereof.

For dental diagnosis and treatment it is necessary to know the relation between the teeth constituting the dental arch of the patient. To this end, it is desired to take a continuous X-ray picture of the dental arch as a whole. For taking such a continuous X-ray picture, it is required to move both the X-ray tube and the film together along the dental arch of a patient without substantially disturbing the relative position of the tube and the film, and the movement must be continuous and smooth. What is more important is that the tube and the film must be moved, with the straight line connecting them always perpendicularly crossing a line tangent to the dental arch at a point thereof whose adjacent area is to be photographed. Unless the above straight line makes a right angle with the tangential line, it will become impossible to take a picture of the object at a position directly opposite thereto, and if the angle between the two lines varies as the X-ray tube and the film are moved together, each area of the dental arch is photographed at a different angle so that it will become of little use to have a continuous picture of the dental arch.

An apparatus which meets the above requirement has been proposed in an application filed simultaneously with the above copending application. In practice, however, the shape of the dental arch considerably differs in different individuals, so that in order to take an accurate continuous picture of the dental arch, it is necessary to change the shape of the ellipse along which the X-ray tube and the film are moved in accordance with the shape of the dental arch of each particular patient to be photographed.

Accordingly, the primary object of the invention is to provide an apparatus for taking an accurate, continuous X-ray picture of the dental arch regardless of difference in the shape thereof between different patients.

SUMMARY OF THE INVENTION

The apparatus of the invention is based on the fact that the dental arch approximates an arc of a geometrical ellipse even though it more or less differs in different persons. Therefore, the arrangement is such that the X-ray tube and the film are moved together along the arcuate path of an ellipse approximating the dental arch, and at any position of their movement the straight line connecting the X-ray tube and the film always makes a right angle with a line tangent to the ellipse at a point where the connecting line crosses the ellipse. The shape of the ellipse is varied with the shape of the dental arch of each individual patient. In practice, since the shape of the dental arch generally corresponds to that of the jaw, the ellipse is varied with the shape of the jaw.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be clearly understood by reading the following description of a preferred embodiment thereof with reference to the accompanying drawings, wherein the same reference symbols in different figures denote corresponding parts, and wherein:

FIG. 1 is a somewhat schematic top plan view showing the principle on which the invention is based;

FIG. 2 is a view similar to FIG. 1 but showing some of the component parts in a different operative position;

FIG. 3 is a somewhat schematic top plan view showing connecting means for adjusting the shape of the ellipse along the arc of which the X-ray tube and the film are moved together;

FIG. 4 is a part-cut-away perspective view of one embodiment of the invention, absent the foregoing means for adjusting the shape of the ellipse;

FIG. 5 is a part perspective view of the connection between the adjustment means and the basic device;

FIG. 6 is a part top plan view of the latter; and

FIG. 7 is a part side view of the same.

Referring first to FIG. 1, which shows the arrangement on which the invention is based, there is shown a reference or base 1 having a slot 2 formed therein. A pin 4 engages in the slot 2 so as to be slidable along the length thereof and is secured to one end of a link or arm 3, the other end of which is pivoted by a pin 5 to one end of a link or arm 6. In the opposite end of the arm 6 there is formed a slot 7 extending a suitable distance along the length of the arm. A pin 8 is fixed on the base 1 on a straight line with the slot 2, and at a suitable distance from one end of the slot 2. The pin 8 engages in the slot 7 formed in the arm 6 so as to be slidable along the length thereof. A pin 9 is pivotally connected at a suitable position on the arm 6, and by means to be later illustrated, pivotably supports a relatively rotatable drive member or arm 10 having a slot 11 formed therein. The previously mentioned pin 4 slidably engages in this slot 11 as well as the slot 2.

On the straight line between the slot 2 and the pin 8, and at a suitable distance from the opposite end of the slot 2, there is another pin 12 fixed to the base 1. In the embodiment of the invention shown in FIGS. 3-7, the position of the pin 12 is variable relative to the pin 8, or the base 1, as shall be described.

Along the sides of the triangle formed by the straight lines connecting the pins 8, 9 and 12, an endless flexible band 13 extends, so that as the band is driven by means to be later illustrated, the pin 9 is moved along. In practice, rotary members to be later illustrated, such as sprocket wheels, are provided on the pins 8, 9 and 12, and the band 13 takes the form of an endless chain engaged with the sprocket wheels. With such an arrangement, slip between the pin 9 and the band 13 can effectively be avoided.

An X-ray tube 21 and a film holder 22 are mounted on the opposite ends of the support arm 10, respectively. The patient is positioned intermediate the X-ray tube and the film holder in such a manner that the major axis of an ellipse approximately conforming to the dental arch of the patient, coincides or is aligned with the straight line connecting the pins 8 and 12, or an extension of the line.

As is easily understood, the sum of the sides of the triangle formed by the lines connecting the pins 8, 9 and 12, is always the same regardless of the position of the pin 9 driven by the band 13. If the distance between the pins 8 and 12 is fixed, the sum of the distances between the pins 8 and 9, and that between the pins 9 and 12, is constant regardless of the position of the pin 9. This means that the pin 9 is moved along the locus of the ellipse 14 with the positions of the pins 8 and 12 as its foci. As seen, the slot 2 coincides with the major axis of the ellipse 14, and in FIG. 1 the arm 10 coincides with the minor axis thereof.

Since the pin 8 slidably engages in the slot 7 of the arm 6, the arm 6 can move longitudinally of itself, so that even when the pin 9 is at the above-mentioned position, the arm 6 can take a desired position corresponding to the position of the pin 9. Since the pin 5 exists on the extension of a line connecting the pins 8 and 9, and the arm 3 connects the pin 5 and the pin 4, which latter pin is always on the major axis of the ellipse 14, the distance between the pins 4 and 5 is kept constant regardless of the positional change of the pin 9. Since the arm 10 connects the pins 4 and 9, the arrangement is also such that when the pin 9 assumes a position on the minor axis of the ellipse 14, the pin 4 assumes a position at the center, that is, the intersection of the major and minor axes of the ellipse, and the arm 10 coincides with the minor axis thereof. In other words, the length of the arm 3, and the position of the pin 4, are so determined that when the pin 9 assumes a position on the minor axis of the ellipse, the arm 10 coincides with that axis.

Suppose that the pin 9 has been moved by driving the band 13 from the position of FIG. 1 to that in FIG. 2. At this position, the pin 9 is still disposed on the ellipse 14, and the distance between the pins 4 and 5 remains unchanged. As shown, the arm 10 crosses the ellipse on a line substantially perpendicular to the tangent to the ellipse at the position of the pin 9. In this case, however, the distance between the pins 4 and 9 changes as the pin 9 is moved. The slots 4, 7 and 11 are provided to enable smooth movement of the arms 3 and 6 in accordance with the above-mentioned distance change.

A patient is positioned between the X-ray tube 21 and the film holder 22, in such a manner that the major axis of the ellipse corresponding to the dental arch of the patient, coincides with the major axis of the ellipse 14, and the patient's face is so directed that his or her dental arch is in parallel with the right-hand half of the ellipse (as viewed in FIG. 1 or 2). In other words, the patient's face is so directed that X-ray is projected from behind the head. That is to say, the X-ray tube is moved transversely behind the patient's head and the film, before the patient's face, and as the X-ray tube is moved in the above manner, the X-ray beam is projected substantially perpendicularly to the dental arch regardless of the position of the X-ray tube. If an X-ray film is placed circumferentially on the cylindrical wall of the film holder 22, and is rotated about its own axis in synchronism with the movement of the X-ray tube, it is possible to take a continuous picture of the dental arch on the film.

Referring now to the embodiment illustrated in FIG. 4, it will be seen that the base 1 has a U-shaped or yoke-like cross section, and is comprised of a pair of rounded, spaced, parallel brackets 40 and 42, interconnected by a bight connection 44 therebetween. The pin 8 extends upright between the brackets, and is fixed to both. The pin 4 is upstanding on the lower bracket 42, at a point adjacent the rounded end 42' thereof; whereas the pin 12 depends from the upper bracket 40, at a point more closely adjacent the rounded end 40' thereof. The arm 10 is slung below the lower bracket, by means of an L-shaped extension 46 upstanding thereon, the outlying end of which has the pin 9 pivotally engaged therein. The pin 9 is pivotally upstanding in the arm 6 therebelow, and connected with the pin 9, as well as with each of the pins 8 and 12, is a sprocket 48 or other means for carrying the chain 13 interconnected among the pins. The chain 13 is driven through the pin 9, by means of a spur gear 50 thereon which is in mesh with a cooperating spur gear 52 on the shaft 54 of a motor 56 mounted on the horizontal leg 46' of the extension.

Also mounted on the extension 46 is a biasing device 58 comprising an elongated rod 59 which is slidably engaged in the vertical leg 46" of the extension, and equipped with a roller 60 at the left-hand or inboard end thereof, which engages the rounded end 42' of the lower bracket. The roller 60 is carried in a sheave block 62, and caged between the block and the vertical leg 46" of the extension is a coiled spring 64, the bias of which maintains the roller against the edge 42' of the bracket, and urges the arm 10, and the pin 9, in the direction outwardly away from the edge 42' of the bracket.

In the above description, it was assumed that the dental arch to be photographed was similar to the right-hand half of the ellipse 14. Dental arches differ in shape between different persons, however, so that it is necessary to change the shape of the right-hand half of the ellipse 14 to resemble in shape the dental arch of the particular person to be photographed. Generally speaking, the dental arch of each person resembles more or less an arc of a geometrical ellipse, so that it is sufficient to change the eccentricity of the ellipse 14 in accordance with the shape of the particular dental arch to be photographed. To this end, either the major or minor axis, or both, must be changed; and to change them, either the distance between the pins 8 and 12, or the sum of the distance between the pins 8 and 9 and that between the pins 9 and 12, may be changed. Moreover, the shape of a dental arch is determined by its width, which in turn approximates the width of the jaw. Therefore, the ellipse 14 may be changed in accordance with the width of the jaw of each individual.

FIG. 3 shows an arrangement constructed in accordance with the invention wherein the ellipse 14 is adjusted by displacing the pin 12 along the major axis thereof in accordance with the width of the patient's jaw. As seen, when the pin 12 is displaced toward the pin 8, the ellipse 14 has a shorter major axis and a longer minor axis. Were the pin 12 displaced away from the pin 8, the ellipse would have a longer major axis and a shorter minor axis. To effect such a relative displacement of the pin 12, a screw rod 31 is provided in alignment with the major axis of the ellipse, and the pin 12 is not fixed on the base, but is movable relative thereto. An internally threaded-through bore is formed in the pin 12, transversely of the axis thereof, so that the rod 31 may be threaded through the bore. As the rod 31 is rotated about its axis, the pin 12 moves along the length of the rod 31, that is, the major axis of the ellipse 14, thereby changing its relative position to the pin 8.

A controller 32 controls the rotation of the rod 31. The controller 32 includes a motor (not shown) adapted to be rotated an amount determined by the change in the distance L between a pair of calipers or levers 33 and 34. To put it in detail, so long as the distance L remains a reference length, the motor does not rotate. If the distance L becomes shorter than the reference length, the motor is rotated in accordance with the difference between the distance L and the reference length, so as to move the pin 12 rightward in FIG. 3; whereas if the distance L becomes longer than the reference length, the motor is accordingly rotated so as to move the pin 12 leftward. The controller may be so designed that a voltage is produced corresponding to the distance L between the two levers 33 and 34, and the voltage is compared with a reference voltage so that the difference in voltage may be used to drive the motor. The construction of such a controller is well known in the art, so that no further explanation should be required.

A patient 35 has his jaw held between the tip ends of the levers 33 and 34, so that the distance L is varied with the width of the jaw. It is not necessary that the jaw be held between the levers, but in fact, any other portion of the face or head, the width of which is proportional to the width of the dental arch, may be held between the levers.

In the arrangement of FIG. 3 the pin 12 is automatically moved in accordance with the distance L. The arrangement may also be such that the width of the dental arch is separately measured, and the pin 12 may be manually moved in accordance with the measured width. Also, instead of displacing the pin 12, the length of the band 13 may be changed for the same purpose.

FIGS. 5-7 illustrate one mode of mounting the pin 12. As seen, the rounded end 40' of the base 1 has a slot 66 therein, and the pin 12 has a poll 68 thereon which is slotted at either side to ride on the base within the slot 66.