Bearing system for cone beam computed tomography
A radiographic imaging apparatus includes elongated rigid guide rails having equivalent symmetrical shapes. Carriages attached to the guide rails are configured to move along a length of the guide rails and to support a portion of the imaging apparatus and to facilitate movement thereof along the guide rails. A first type spherical bearing assembly allows a gimbaled connection thereto while allowing substantially no axial movement. A second type spherical bearing assembly allows a gimbaled connection thereto while allowing a limited amount of axial movement. Frame mounts are each attached to one of the first type and second type spherical bearing assemblies to facilitate movement having a one sided tolerance along the guide rails.
1. A radiographic imaging apparatus having an x-ray source and x-ray detector, the apparatus comprising:
elongated rigid guide rails having equivalent symmetrical shapes and spaced apart substantially in parallel;
carriages each attached to one of the guide rails, wherein the carriages are configured to move along a length of the guide rails;
a first type spherical bearing assembly attached to a first one of the carriages which is attached to a first one of the guide rails, the first type spherical bearing assembly configured to allow a gimbaled connection thereto while allowing substantially no axial movement, the axial movement perpendicular to the first one of the guide rails;
a second type spherical bearing assembly attached to a second one of the carriages which is attached to a second one of the guide rails, the second type spherical bearing assembly configured to allow a gimbaled connection thereto while allowing a limited amount of axial movement perpendicular to the second one of the guide rails; and
frame mounts each attached to one of the first type and second type spherical bearing assemblies, the frame mounts each configured to support a portion of the imaging apparatus and to facilitate movement thereof along the guide rails.
2. The apparatus of claim 1 , wherein the portion of the imaging apparatus is prevented from moving substantially away from the first one of the guide rails as it moves along the guide rails by action of the first type spherical bearing assembly, and wherein the portion of the imaging apparatus is allowed to move substantially away from or toward the second one of the two guide rails as it moves along the guide rails by action of the second type spherical bearing assembly.
3. The apparatus of claim 1 , wherein the first type spherical bearing assembly comprises:
a partially spherical portion having an opening therethrough; and
a flanged cylindrical extension through the opening, wherein a length of the extension is about equal to a length of the opening through the spherical portion, and wherein a flange at a distal end of the extension abuts the spherical portion to prevent the axial movement of the spherical portion.
4. The apparatus of claim 1 , wherein the second type spherical bearing assembly comprises:
a partially spherical portion having an opening therethrough; and
a flanged cylindrical extension through the opening, wherein a length of the extension is greater than a length of the opening through the spherical portion, and wherein a flange at a distal end of the extension prevents the spherical portion from traveling off the end of the extension but allows limited movement of the spherical portion along the extension.
5. The apparatus of claim 1 , wherein the guide rails are shaped in the form of equivalent symmetrical curves.
6. The apparatus of claim 1 , wherein the guide rails are shaped in the form of equivalent symmetrical arcs.
7. The apparatus of claim 1 , wherein the guide rails are shaped in the form of straight guide rails.
8. The apparatus of claim 1 , wherein the limited amount of axial movement perpendicular to the second one of the guide rails about 10 mm or less.
9. The apparatus of claim 1 , wherein the carriages are configured to slide along a length of the guide rails.
10. The apparatus of claim 1 , wherein the frame mounts are each configured to support the source and detector and to facilitate movement thereof along the guide rails.
11. The apparatus of claim 10 , wherein the frame mounts are each configured to support the source and detector and to facilitate bidirectional vertical movement thereof along vertical, linear guide rails.
12. The apparatus of claim 10 , wherein the frame mounts are each configured to support the source and detector and to facilitate revolving movement thereof along arc shaped guide rails.