Claims
- 1. A film drive mechanism for moving an x-ray film past an x-ray slit at a variable rate of speed as a function of the shape of a desired focal trough while the film drive mechanism including the x-ray film is being moved about an object to be x-rayed, comprising, in combination:
- a film holder having an x-ray slit;
- a movable film cassette for mounting in said film holder, said film cassette adapted to support and move an x-ray film past said slit;
- motor means connected to drive said film cassette, said motor means including a rotatable shaft and a housing; and
- means coupled between said shaft and housing to vary the speed of rotation of said shaft with respect to said housing by selectively rotating said housing with respect to said shaft as a function of the shape of a desired focal trough.
- 2. The film drive mechanism of claim 1, wherein said last mentioned means includes means for mounting said housing to float with respect to said shaft, and a sloped cam connected to rotate with said shaft and to cause selected movement of said housing with respect to said shaft during rotation of said shaft.
- 3. The film drive mechanism of claim 2 wherein said sloped cam varies in slope between adjacent circumferential positions in accordance with the shape of the desired focal trough.
- 4. A method of varying the speed of movement of an x-ray film past an x-ray slit as a function of the shape of an object to be x-rayed while the x-ray film is being moved about the object to be x-rayed at a substantially constant speed, comprising the steps of:
- connecting a motor having a housing and a shaft that rotates with respect to the housing to move said x-ray film past said x-ray slit; and
- varying the relative motion of the shaft with respect to the motor housing to vary the speed of movement of said x-ray film as a function of the shape of the object to be x-rayed.
- 5. The method of claim 4 wherein the last mentioned step is provided by utilizing a sloped cam connected between the shaft and housing to vary the speed of rotation of the shaft with respect to the housing of the motor.
- 6. The film drive mechanism of claim 1 wherein said housing mounting means includes means for following the rotation of said sloped cam to move the motor housing with respect to the motor shaft during rotation of the shaft as a function of the slope of said sloped cam.
- 7. The film drive mechanism of claim 6 further including a first pulley mounted on said shaft, a second pulley rotatably mounted to support said sloped cam, and an endless member connected to said first and second pulleys for rotation, and wherein said means for following the rotation of said sloped cam includes a plate mounted adjacent one end to pivot about the motor shaft and connected to said motor housing, and a follower wheel mounted on said plate to follow the rotation of said sloped cam and cause said motor housing to selectively pivot about said motor shaft.
- 8. In a panoramic radiographic apparatus including a circular rotatable disc having an x-ray source and a film holder mounted thereon for movement along a circular path about an object to be x-rayed, the improvement comprising a film drive mechanism mounted in said film holder for moving an x-ray film past an x-ray slit in said film holder at a variable rate of speed as a function of the shape of a desired focal trough, comprising, in combination:
- a movable film cassette for mounting in said film holder, said film cassette adapted to support and move an x-ray film past said slit;
- motor means connected to drive said film cassette, said motor means including a rotatable shaft and a housing; and
- means coupled between said shaft and housing to vary the speed of rotation of said shaft with respect to said housing by selectively rotating said housing with respect to said shaft as a function of the shape of a desired focal trough.
- 9. The film drive mechanism of claim 8 wherein said last mentioned means includes means for mounting said housing to float with respect to said shaft, and a sloped cam connected to rotate with said shaft and to cause selected movement of said housing with respect to said shaft during rotation of said shaft.
- 10. The film drive mechanism of claim 9 wherein said sloped cam varies in slope between adjacent circumferential positions in accordance with the shape of the desired focal trough.
- 11. The film drive mechanism of claim 10 wherein said housing mounting means includes means for following the rotation of said sloped cam to move the motor housing with respect to the motor shaft during rotation of the shaft as a function of the slope of said sloped cam.
- 12. The film drive mechanism of claim 11 further including a first pulley mounted on said shaft, a second pulley rotatably mounted to support said sloped cam, and an endless member connected to said first and second pulleys for rotation, and wherein said means for following the rotation of said sloped cam includes a plate mounted adjacent one end to pivot about the motor shaft and connected to said motor housing, and a follower wheel mounted on said plate to follow the rotation of said sloped cam and cause said motor housing to selectively pivot about said motor shaft.
- 13. A film drive mechanism for moving an x-ray film past an x-ray slit at a variable rate of speed as a function of the shape of a desired focal trough while the film drive mechanism including the x-ray film is being moved about an object to be x-rayed, comprising, in combination:
- a film holder having an x-ray slit;
- a movable film cassette for mounting in said film holder, said film cassette adapted to support and move an x-ray film past said slit;
- motor means connected to drive said film cassette, said motor means including a rotatable shaft connected to rotate said film cassette to move said film past said slit;
- first pulley means connected to said shaft to rotate therewith;
- second pulley means mounted for rotation with respect to said housing;
- means drivenly connecting said first and second pulley means;
- a sloped cam which varies in slope between adjacent circumferential positions in accordance with the shape of the desired focal trough said cam being mounted for rotation on said pulley;
- means for mounting the housing of said motor to float with respect to the film holder and with respect to the shaft of said motor; and
- means coupling said mounting means and said sloped cam so that the rotational position of said motor housing with respect to said shaft is a function of the slope of said sloped cam.
- 14. The film drive mechanism of claim 13 wherein said means for mounting the housing of said motor to float with respect to the film holder is a plate pivotly mounted on one end on the motor shaft and rigidly connected to said motor housing so that rotation of said plate about said shaft causes relative rotation between said shaft and housing.
- 15. The film drive mechanism of claim 14 wherein said means coupling said mounting means and said sloped cam includes a follower wheel mounted on said plate and urged against said cam to follow the rotation thereof.
Parent Case Info
This is a division of application Ser. No. 429,482, filed Jan. 2, 1974 now U.S. Pat. No. 3,908,126.
US Referenced Citations (4)
Divisions (1)
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Number |
Date |
Country |
Parent |
429482 |
Jan 1974 |
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