Abstract:
The gantry of a tomography apparatus has a drum that is rotatable around an axis. The drum carries at least one component mounted thereon. The component is mounted on the drum by a mounting arrangement that resolves a centrifugal force acting on the component into a radial force vector and a substantially axially proceeding force vector. The mounting of the component is thereby made less susceptible to breakage due to the high centrifugal forces that occur upon rotation of the gantry.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention concerns a tomography apparatus, in particular an x-ray computed tomography apparatus.  
         [0003]     2. Description of the Prior Art  
         [0004]     A conventional x-ray computed tomography apparatus comprises a gantry with a drum that can be rotated around a patient bed, which carries, among other things, x-ray source and a detector disposed opposite each other. In x-ray computed tomography systems of newer design, the drum is rotated with a considerable speed of up to 180 revolutions/minute. Centrifugal forces equal 20 to 30 times the acceleration due to gravity thereby act on the components housed in or carried by the drum. As a result, fastening elements with which the components are mounted to the drum subjected to a particularly high stress. Fastening elements may break and causing a component to detach from the drum. This can lead to damage to the x-ray computed tomography or to endangerment of personnel in its vicinity.  
       SUMMARY OF THE INVENTION  
       [0005]     An object of the present invention is to avoid the disadvantages in a tomography apparatus wherein the components attached to the drum are always securely and reliably retained given exposure to high centrifugal forces.  
         [0006]     This object is achieved according to the invention by a computed tomography apparatus having a drum mounted component, wherein the component is mounted on the drum such that a centrifugal force acting on it is the resulting force of a radially-proceeding vector and a substantially axially-proceeding vector, the substantially axially-proceeding vector being aligned on a support surface on the drum. Because the component is attached so that, given a rotation, the centrifugal force acting on it also has a substantially axial vector, the component is forced in the axial direction onto the support surface on the drum by this vector. The component is thus held more firmly on the drum as the centrifugal forces acting on it increase. As a consequence, possible fastening elements provided to secure the component are not stressed with increasing centrifugal force but instead are less stressed. In the operation of the tomography apparatus, an unwanted detachment of components can no longer occur.  
         [0007]     In an embodiment, the support surface is on the drum base. It can be oriented transversally to the drum base in the direction of the drum cladding. Such a surface oriented transversely on the drum base can be produced with the drum base in a one-piece formation. It can also be mounted on the drum base, for example in the form of a shim fashioned as a support element.  
         [0008]     The component itself also can exhibit a suitable sloped surface. In this case, the support surface on the gantry base is fashioned flat in the radial direction.  
         [0009]     According to a further embodiment, a further support surface for support of the component is provided on an inner wall of the drum cladding. The further support surface preferably is oriented at an angle from the inner wall in the direction of the drum opening. The component can be supported on the further support surface such that it can move along rails in an essentially axial direction. This enables a movement of the components in the direction of the drum base. Such a movement can be caused by the centrifugal forces acting on the components. In a further embodiment, the movement is permitted only in the direction of the drum base, but not in the direction of the drum opening. For this purpose, for example, a projection jutting radially inwardly can be provided on the further support surface, the projection allowing a movement of the component only in the direction of the drum base.  
         [0010]     According to a further embodiment, the component can have a first profile and a second profile corresponding to the first profile on a second support surface, such that the component can be connected on the second support surface by shifting the first profile into the second profile. The addressed profiles, for example, can be profiles formed as dovetails, grooves and corresponding tongues and the like. In a similar manner, profiles corresponding to one another can also be provided on the first support surface as well as on the components. They can also, for example, be groove and/or tongue profiles.  
         [0011]     According to a further embodiment, the first profile and the second profile are fashioned such that the components are supported counter to the rotational direction of the drum. For example, for this purpose webs jutting radially inwards, between which the component is accommodated, can be provided on the further support surface. Given an acceleration and/or deceleration of the drum, such webs or similarly fashioned supports counteract the inertia of the component and support, and support these counter to the rotation direction of the drum.  
         [0012]     A first centering element and a second centering element corresponding thereto are provided on the support surface, such that the component can be supported in a self-centering manner on the support surface upon exposure to centrifugal force. It is thereby ensured that the component always stays in an exact, appropriate mounting position. This is particularly important in x-ray computed tomography systems in which the exact position of the radiator and of the oppositely arranged detector has significant influence on the image quality.  
         [0013]     The component can be fastened on the drum with at least one fastening element. This can be a screw, bolt or the like. According to the present invention, the fastening element essentially serves to secure the component, but not to absorb the forces on the drum that are caused by the centrifugal forces acting on the component. As a consequence, fastening elements that are dimensioned smaller or weaker (in comparison with conventional tomography apparatuses can be used. 
     
    
     DESCRIPTION OF THE PRIOR ART  
       [0014]      FIG. 1  is a partial radial section through a gantry drum in accordance with the invention, in a first embodiment.  
         [0015]      FIG. 2  is an axial section according taken along section line A-A′ in  FIG. 1 .  
         [0016]      FIG. 3  is a schematic axial section of a further embodiment of the profile shown in  FIG. 2 .  
         [0017]      FIG. 4  is a schematic axial section of a further embodiment of the profile shown in  FIG. 2 .  
         [0018]      FIG. 5  is a sectional view taken along section line B-B′ in  FIG. 4 .  
         [0019]      FIG. 6  is a schematic axial section of a further embodiment of the profile shown in  FIG. 2 .  
         [0020]      FIG. 7  is a partial radial section through a second embodiment of a gantry drum according to the invention.  
         [0021]      FIG. 8  is a partial radial section through a third embodiment of a gantry drum according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]      FIG. 1  shows a partial radial section of a drum  1  of a tomography apparatus, the gantry  1  being rotatable around an axis A. The drum  1  is normally a rotatable part of a gantry of a known computer tomography apparatus (not shown here in detail). The drum  1  comprises a drum base  2  that, for example, is fashioned in the form of an annular ring. A circumferential drum shell  3  extends in the axial direction from a circumferential edge of the drum base  2 . A first support surface  4  provided in the region of the circumferential edge of the drum base  2  is slanted with regard to the drum base  2  and projects radially inwardly. With the drum base  2 , the first support surface  4  forms a first acute angle that opens toward the circumference edge of the drum base  2 .  
         [0023]     A second support surface  5  projecting radially inwardly is provided on an inner wall of the drum shell  3 . The second support surface  5  is slanted relative to the inner wall of the generated surface  3 . With the inner wall, it forms an acute angle that opens toward an opening of the drum  1 . A component  6 , for example an x-ray radiator, is supported at its housing on the first support surface  4  and the second support surface  5 . The first support surface  4  can be a component of a first support element  4   a  which is mounted on the drum base  2 . In the same manner, the second support surface  5  can be a component of a second support element  5   a  which can be mounted on the inner wall of the drum shell  3 . The support surfaces  4 ,  5  can also be produced in a one-piece formation with the drum base  2  and/or the drum shell  3 .  
         [0024]     As can be seen from  FIG. 2 , the component  6  is provided with a first profile  7  that interacts [cooperates] with a second profile  8  for fastening purposes. The second profile  8  is two rails extending from the drum base  2 . For securing, the component  6  can be fastened in the region of the free ends of the rails, for example with fastening elements  9  in the form of a spring hinge.  
         [0025]     Due to the slanted (with regard to a centrifugal force g acting on component  6  given a rotation of the drum  1 ) supports of the component  6  effected by the first support surface  4  and the second support surface  5 , this centrifugal force g is decomposed into two components z.  
         [0026]     The radial vector r′, the axial vector z′ and the resulting force g are shown in  FIG. 1 . As a result of the force exerted on the component  6  by the axial vector z′, with increasing centrifugal forces this component  6  is forced against the first support surface  4  and against the second support surface  5 . The fastening device acting in the form of the first profile  7  and in the form of the second profile  8  as well as the fastening elements  9  is unstressed given a rotation of the drum  1 . The forces acting on the components  6  are absorbed by the first support surface  5  and the second support surface  5 .  
         [0027]     In a schematic axial section,  FIG. 3  shows a further embodiment of the first profile  7  and the second profile  8 . In this case, the profiles are fashioned like dovetails. The second profile  8  is fashioned as one piece with the second support element  5   a.    
         [0028]      FIG. 4  through  6  show further embodiments of the first profile  7  as well as or the second profile  8 . In these respective embodiments, a second support element  5   a , which has the second support surface  5  thereon with the second profile  8  therein, is mounted on the inner wall of the drum shell  3 . In the embodiment shown in  FIGS. 4 and 5 , the second profile  8  is formed by two webs  10  extending along the edge, the webs  10  supporting the component  6  counter to rotational movement of the drum  1 . The embodiment shown in  FIG. 6 , in which the first profile  7  is fashioned in the form of an axially proceeding V-shaped rib, acts in a similar manner. In this case, the second profile  8  is fashioned correspondingly in the shape of a likewise axially extending V-shaped recess.  
         [0029]     In the second embodiment of the drum  1  shown in  FIG. 7 , the component  6  exhibits a first profile  7  formed by a web extending in the circumferential direction of the drum  1 . The second profile  8  is fashioned in the shape of a corresponding recess. In this exemplary embodiment, moreover, the component  6  is non-positively mounted on the drum base  2  by means of two fastening elements  11  (here in the form of screws).  
         [0030]     In the drum  1  schematically shown in  FIG. 8 , a centering mandrel  12  extends from the drum base  2  and protrudes into a corresponding recess  13  in the component  6 . The component  6   e —as in the aforementioned exemplary embodiments—has a second support surface  5  that abuts a second support element  5   a  such that it can slide in the axial direction. Under the influence of centrifugal forces acting on the component  6 , the component  6  is forced in the direction of the centering mandrel  12  as a result of the axial vector z. This embodiment thus is self-centering.  
         [0031]     With the inventive apparatus, the component  6  can be securely held at a predetermined mounting location in the drum  1  of a tomography apparatus with extreme precision. Due to the supporting of the component  6  on the first slanted surface  4  and the second slanted surface  5 , the disadvantageous effects of centrifugal forces as occur in the prior art, can be prevented. Breakage of fastening elements, and thus an unwanted detachment of the component  6  from the drum  1 , thus can be prevented.  
         [0032]     As noted above, the component  6  is fashioned with regard to the first support surface  4  and the second support surface  5  so that the support surfaces  4 ,  5  abut with a positive fit. This manner of mounting the component  6  on the drum  1  can be simply accomplished. For example, the component  6  merely has to be inserted, by means of the first profile  7  provided thereon, into the second profile  8  provided at the drum  1 , and secured to the drum  1  by one or more fastening elements  9 ,  11 ,  14 . In the self-centering embodiment, an extremely precise mounting of the component  6  on the drum  1  can be achieved in a simple and fast manner.  
         [0033]     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.