Abstract:
A support system for a scanner comprises a frame and a drum. The drum is made of tempered steel and is mounted on the frame by a roller system. The roller system comprises rollers of hardened steel, or having roller surfaces of hardened steel, that allow the drum to rotate about a rotationally symmetrical axis of the drum. A radiation source and one or more detectors can be secured to the drum for a scanner. Because that the drum is made of tempered steel and the rollers have surfaces of hardened steel, the drum can rotate at a high speed without increasing vibrations, thus allowing examination times of the scanner to be short and preventing vibration-related background signals. Also, noise occurring during use of the scanner is reduced.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a support system for a scanner, comprising a frame and a drum, wherein mounting of the drum on the frame allows a rotation of the drum about the axis of rotational symmetry thereof and wherein a scanner system can be attached to the drum. 
       PRIOR ART 
       [0002]    Support systems, of the type mentioned above, for scanners are known. In particular, the scanner system can be an X-ray radiation source and one or more corresponding detectors. By way of example, DE 196 29 931 C2 (Siemens) describes an X-ray computed tomography scanner with an annular gantry that is rotatably mounted in a frame which has rollers for the radial and axial guidance of the gantry. In this case, the axles of the rollers are offset with respect to one another by 90° and run on the outer or lateral faces of rails that enclose the gantry along the circumference thereof. The rails are connected to the gantry with a rubber layer disposed therebetween. 
         [0003]    DE 195 81 512 C2 (Analogic) relates to an X-ray beam tomography system with a pivotable frame, on which a rotatable drum is arranged. Functional elements of the system (at least the X-ray source) are attached to the drum. The drum is mounted on carriages that comprise tandem rollers which are rotatable about an axis that is parallel to the rotational axis of the drum. The bearing surfaces of the rollers and the carriage are manufactured from an elastic material and thus dampen a transmission of vibrations between the frame and the drum, and absorb cyclical temperature variations of the drum. The peripheral, annular component of the drum is formed by a rolled extruded part made of a light material such as e.g. aluminum or an Mg—Al alloy. The component forms a uniform, circular band with edge lips protruding in the transverse direction, said edge lips extending outward in the radial direction. In addition to the carriage, the device has at least three pairs of elastic rollers, which have been provided with tires, which are arranged on the frame for rotation along radial lines. These rollers contact the lateral edges of the edge lips of the drum and hence guide the latter in the axial direction. The drum is driven by a motor which is coupled to one of the tandem rollers. 
         [0004]    U.S. Pat. No. 7,010,081 B2 (Philips) shows a CT scanner with a rotating gantry and a stationary gantry, wherein the rotating gantry has an encircling mounting rail, which has raceways tilted toward one another for axial and radial mounting. Conical rollers arranged on the stationary gantry interact in pairs with the raceways of the mounting rail. A drive motor is coupled to one of the rollers for driving the rotating gantry. The roller bearings consist of a metallic core, more particularly steel, and a tire-like polymer coating, more particularly made of polyurethane, which creates cushion-like damping while at the same time having a rigid mounting. 
         [0005]    It was found that the rotational movement of the gantry cannot be controlled precisely in such devices and that undesired flexing of the gantry may occur. 
         [0006]    U.S. Pat. No. 5,109,397 (Analogic) shows a computed tomography scanner with an annular gantry. The latter is attached to a vertical support frame such that it can pivot about a horizontal axis, wherein this support frame can be linearly displaced along rails relative to an instrument base. A lever whose length can be adjusted is attached between the support frame and the gantry and enables the pivoting of the gantry. The gantry comprises an external annular frame and a rotatable inner part that is attached to the inside of the frame by antifriction bearings. 
         [0007]    This solution has a complicated design. 
         [0008]    U.S. Pat. No. 6,188,743 B1 (Analogic) relates to a computed tomography scanner with an annular disk, the circumferential edge of which is provided with grooves so that the disk can serve as a belt pulley which can be driven by a drive motor via a tensioned belt. The disk is mounted on a stationary frame, either in the region of its center of gravity via spacers or on the circumference by conventional four-wire mounts. The disk can be manufactured from a light, stiff material such as e.g. aluminum or a magnesium-aluminum alloy and is preferably produced by precision casting and is subsequently hardened and subjected to finishing. 
         [0009]    Conventional wire bearings have soldering points of the wires, which lead to vibrations in the case of a high rotational speed of the disk. These vibrations cause a background signal in the tomographic recordings. 
       DESCRIPTION OF THE INVENTION 
       [0010]    It is an object of the invention to create a support system that is part of the technical field mentioned at the outset, which enables short examination times but nevertheless has a cost-effective design. 
         [0011]    The solution to the object is defined by the features of claim  1 . According to the invention, the drum substantially consists of heated and tempered steel and/or has bearing surfaces made of hardened steel and a roller system with rollers is attached to the frame, by means of which roller system the drum can be rotated about the axis of rotational symmetry of the drum. The rollers consist of hardened steel or are at least equipped with bearing surfaces made of hardened steel. 
         [0012]    As a result of the drum being produced from heated and tempered steel and as a result of the rollers, which have at least bearing surfaces made of hardened steel, it is possible to achieve increased rotational speeds of the drum, without increased vibrations of the drum occurring at the same time. The rotational speeds achieved in this manner enable short examination times of the scanner because vibration-dependent background signals are avoided. Moreover, disadvantageous noise-development during the examination, which would decrease the comfort of the users of the scanner, is avoided. 
         [0013]    The rollers particularly preferably consist of ball-bearing steel and are hardened through. 
         [0014]    Mounting the drum on a roller system so that increased rotational speeds of the drum are made possible can be brought about in a simple and cost-effective manner. 
         [0015]    Therefore the support system, according to the invention, for scanners is particularly suitable for applications in which, in a cost-effective manner, a short examination time is desired. In addition to computed tomography in the medical field, this specifically also is the case in baggage handling at airports or at customs. 
         [0016]    The drum produced from heated and tempered steel is advantageously produced without joints, more particularly rolled or forged without joints. This prevents vibrations that would be created if one of the rollers passes over a joint in the drum. This enables a further increase in the rotational speed of the drum, without an undesired increase in the vibrations. 
         [0017]    On the lateral face, the drum preferably comprises a rail (or bearing surface) on which the rollers of the roller system run. Together, this rail and the drum are advantageously formed integrally from the same material. Moreover, the rail preferably has induction hardened bearing surfaces. 
         [0018]    In a preferred embodiment, the weight of the drum is borne by at least two roller pairs, which are each arranged moveably relative to the frame along a track oriented tangentially with respect to the drum (and perpendicularly to the drum rotational axis). The moveable arrangement enables a self-regulating, uniform distribution of the weight of the drum on the roller pairs. Moreover, small changes in size and shape of the drum due to temperature can be compensated for. A very small tangential displacement path of the rollers of less than e.g. 0.5% of the drum diameter has already proven to be sufficient. It is advantageous for the rollers to be free and movable along the track with as little friction as possible; however, alternatively, it is also possible to provide e.g. springs, which bring the rollers into a predetermined zero position if there are no additional forces. 
         [0019]    Instead of roller pairs, provision can be made for spaced apart and fixedly arranged individual rollers, with the weight of the drum being borne by these. 
         [0020]    It is preferable for two of the rollers to be attached to a roller support in each case, wherein the roller support is mounted on a linear guide attached to the frame in order to enable the tangential mobility. By mounting the drum on respectively two tangentially spaced apart rollers, the forces exerted by the drum on the roller pairs in substantially a radial direction are transferred in an optimum manner onto the roller support and, from the latter, onto the linear guide. Moreover, a damping element is particularly preferably arranged between the roller support and the linear guide. This damping element does not provide an additional movement possibility for the rollers but serves to minimize the transmission of vibrations onto the frame. As a result, the noise development can be greatly reduced. By way of example, the damping element can be embodied as a plastic coating on the linear guide. 
         [0021]    In a further embodiment, the weight of the drum is borne by a plurality of roller pairs, which are each mounted on a rocker. Here, both the rotational axes of the rockers and the rotary axles of the rollers are oriented parallel to the axis of rotational symmetry of the drum. The rotational axis of the rockers is preferably on the mirror-symmetric axis between the two rollers in each case, said axis running perpendicular to the connecting line between the two rollers. This mounting is advantageous in that there is a self-regulating, uniform distribution of the weight of the drum on the rollers mounted on the rockers. Additionally, an advantage of mounting like this is that small changes in size and shape of the drum due to temperature are compensated for. Since this mounting of the drum adapts perpendicularly to the axis of rotational symmetry of the drum without, in doing so, providing the drum with a translational degree of freedom perpendicular to the axis of rotational symmetry of the drum, this also suppresses vibrations that may be created at high rotational speed of the drum due to a non-correspondence between the center of gravity of the drum and the rotational axis of the drum. 
         [0022]    As an alternative to this mounting, mounting on only two rollers or mounting of the drum on a plurality of eccentrically mounted individual rollers is also feasible. 
         [0023]    It is preferable for one or more rollers which do not bear the weight of the drum to be mounted eccentrically or to be under resilient pretension. In the following text, eccentric mounting is understood to mean eccentric mounting of the roller axle, with the eccentric being set once during assembly and remaining fixed thereafter. Resilient pretension is achieved by a spring element that places the roller onto the drum circumference. The only function of these rollers is to ensure play-free mounting of the drum. Since the rollers either are produced entirely from hardened steel or have at least one bearing surface made of hardened steel, eccentric mounting of the corresponding rollers or a resilient pretension is the best solution for this. 
         [0024]    As an alternative to this, use can also be made of one or more rollers that consist of soft material. Such rollers adapt to the size and shape of the drum without needing to be mounted eccentrically for this purpose. 
         [0025]    The drum is preferably held in the frame by guide rollers attached to the frame. To this end, the guide rollers run on both sides of the rail, with the axles of said guide rollers being aligned radially with respect to the drum. These guide rollers consist entirely of hardened steel (more particularly ball-bearing steel) or are equipped with at least one bearing surface made of hardened steel. 
         [0026]    Compared to a likewise feasible arrangement in which the guide rollers run on the end faces of the drum, the guide-roller arrangement of the invention is advantageous in that the instruments and components of the scanner can also be attached to the end faces of the drum. 
         [0027]    Compared to a further feasible arrangement of the rollers and the guide rollers on more than one rail on the lateral face of the drum, this embodiment of the invention is furthermore advantageous in that space is saved on the lateral face of the drum, and hence the scanner can be built in a space-saving manner. 
         [0028]    It is preferable for the drum to be mounted without play by virtue of the guide rollers on at least one side of the rail being mounted eccentrically or being under resilient pretension. This enables play-free guidance of the drum, and hence quiet and uniform running with little mechanical load. 
         [0029]    If the drum has obliquely leaning bearing surfaces, e.g. two areas respectively oriented at an angle of 45° with respect to the rotational axis, which thus include an angle of 90°, then the rollers can simultaneously also assume the guidance function for the drum; separate guide rollers become superfluous. In the case of such rollers with a guidance function, the bearing surfaces are advantageously ground like a ball such that differential slip is prevented in the region of the running contact. Rollers arranged at the top (which primarily have a guidance function) advantageously are eccentrically mounted or under resilient pretension. 
         [0030]    The rotational movement of the drum is preferably driven by a driving belt that runs around the drum. Here, this can be any type of driving belt, e.g. a V-belt, a flat belt or a toothed belt, and the driving belt can run in a groove in the lateral face of the drum or else directly on the lateral face of the drum. The lateral face of a drum, which is provided with a rail, preferably has an integrated belt pulley next to the rail; in particular, this region of the lateral face has an appropriate profile. 
         [0031]    The advantage of the drive via a driving belt is that there is good force transmission onto the drum. Alternative drive solutions, such as e.g. the drive by means of a driving roller or a drive roller require slip-free contact between the rail and the driving roller. Such a drive can only be achieved by a special bearing surface of the driving roller and/or by strong pressure of the driving roller against the drum. The former would have a negative influence on the rotational behavior of the drum while the latter would cause great energy loss as a result of friction. 
         [0032]    The motor for the driving belt is preferably attached to the frame. The advantage of this is that neither the control nor the power supply for the motor needs to be routed from the frame to the drum. 
         [0033]    The driving belt is preferably tensioned by means of a tension roller that is attached to the frame. This tension roller is advantageous in that the driving belt can be tensioned with a desired force even during operation of the support system and in that the driving belt can easily be replaced in the case of repairs. 
         [0034]    A slip ring is preferably attached to the external side of the drum and establishes the required electrical contacts to the instruments and components that are attached to the drum, with a brush attached to the frame establishing the contacts to the slip ring. As an alternative to this, it is also possible for the required electrical contacts to be attached to the drum and the slip ring to be fixedly attached to the frame. 
         [0035]    The contact to the slip ring on the external side of the drum preferably ensures the precise positioning of the drum. 
         [0036]    The advantage of this type of positioning is that, unlike determining the position of the drive motor, it takes place directly on the drum and hence directly establishes the position thereof. 
         [0037]    The instruments and components are preferably attached to holes in the drum. 
         [0038]    This type of attaching instruments and components is advantageous in that, according to the invention, a standard embodiment of the support system can be used for different scanners and in that such a scanner can easily be upgraded with additional or newer instruments and components. 
         [0039]    Furthermore, this type of attachment saves weight because there is no need for heavy intermediate pieces. 
         [0040]    An alternative option for attaching the instruments and components to the drum consists of attaching a disk to the drum, with the instruments and components being fixedly mounted on said disk. In addition to the disk, it is also possible for further elements to be attached to the drum, e.g. an inner ring that interacts with the driving belt. Hence, the drum as it were acts as a raceway, onto which the further elements are added. 
         [0041]    Further advantageous embodiments and feature combinations of the invention emerge from the following detailed description and the totality of the patent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    In the drawings used to explain the exemplary embodiment: 
           [0043]      FIG. 1  shows an oblique view of a first support system, according to the invention, for a scanner; 
           [0044]      FIG. 2  shows a frontal view of the support system according to the invention, 
           [0045]      FIG. 3  shows a further oblique view of the support system according to the invention; 
           [0046]      FIG. 4  shows an oblique view of a second support system, according to the invention, for a scanner; 
           [0047]      FIG. 5  shows a detailed view from a first side of an installed roller support with two rollers; 
           [0048]      FIG. 6  shows a detailed view from a second side of the roller support; 
           [0049]      FIG. 7  shows an oblique view of the roller support; 
           [0050]      FIG. 8  shows a cross section through the roller support; 
           [0051]      FIG. 9  shows an oblique view of a third support system, according to the invention, for a scanner; 
           [0052]      FIG. 10  shows a detailed view of an upper guide unit; and 
           [0053]      FIG. 11  shows a detailed view of a lower guide unit. In principle, equivalent parts in the figures have been denoted by the same reference signs. 
       
    
    
     WAYS OF IMPLEMENTING THE INVENTION 
       [0054]      FIG. 1  shows an oblique view of a support system, according to the invention, for scanners. The illustrated support system comprises a frame  1 , which consists of a steel plate and which has been attached standing up in a stand (not illustrated). Situated within this frame  1  there is an opening, in which a substantially hollow-cylindrical drum  2  has space, with the axis of rotational symmetry thereof being perpendicular with respect to the plane of the steel plate of the frame  1 . The diameter of this drum  2  is approximately eight times greater than the length of the drum  2 . The drum  2  is forged without joints from heated and tempered steel C45 (pursuant to DIN EN 10027-1). A rail  3  with a rectangular cross section, which runs in the center of the lateral face of the drum  2 , encompasses the drum  2  in an annular manner. Together with the drum  2 , the rail  3  is forged from one part. The three free faces of the rail are induction hardened (58 (0/+4) HRC). The drum  2  is mounted in the frame  1  such that the annular rail  3  and the frame  1  substantially lie in one plane. Here, on the external side (i.e. the side facing the frame  1 ), the annular rail  3  is borne at three points on lower rollers  4  and an upper roller  5 . These lower and upper rollers  4 ,  5  are either manufactured completely from through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1) or else they have bearing surfaces made of through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1). The lower rollers  4  and the upper roller  5  are mounted on the frame  1 . In a polar coordinate system, in which the angular coordinate starts at 0 degrees at the top-most point in the opening of the frame  1  and then rotates in the plane of the frame  1  in a clockwise direction, respectively one pair of the lower rollers  4  is mounted on the frame  1  at 135° and at 225°. Since the frame  1  stands vertically, the weight of the drum  2  is borne by these two pairs of lower rollers  4 . Both pairs of the lower rollers  4  are mounted on a rocker  6  in a fitting recess in the opening of the frame  1  with the axles of the lower rollers  4  being parallel to the axis of rotational symmetry of the drum  2  (see  FIG. 3 ; in the view of  FIG. 1 , these rockers  6  are situated on the rear side of the frame  1 ). The rockers  6  can rock about an axis that is parallel to the axis of rotational symmetry of the drum  2 . The axis of the rockers  6  lies in the mirror-symmetric plane of the rockers  6 , which is situated perpendicularly with respect to the connecting line between the two axles of the lower rollers  4 . The rocking motion made possible by the rockers  6  ensures that the weight of the drum  2  is uniformly distributed over all lower rollers  4 . 
         [0055]    The upper roller  5  is mounted eccentrically at 0° of the angular coordinate in the aforementioned polar coordinate system and clamps the drum  2  between itself and the lower rollers  4 . Together, the upper and lower rollers  4 ,  5  prevent a displacement of the drum  2  in the plane of the frame  1  and at the same time permit a rotational movement of the drum  2  about the axis of rotational symmetry thereof. 
         [0056]    So that the rail  3  of the drum  2  and the frame  1  remain in one plane, guide rollers  7  are attached to the frame  1 ; these guide rollers consist of through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1) or have at least bearing surfaces made of through-hardened ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1). These guide rollers  7  are respectively arranged in pairs, wherein, per pair, one guide roller  7  is attached on one side of the face of the frame  1  (and the rail  3 ) and the other guide roller  7  is attached on the other side of the frame  1  (and the rail  3 ) and runs on the respective side face of the rail  3 . Overall, three pairs of guide rollers  7  are arranged symmetrically around the drum  2  at angular coordinates 45°, 180° and 315° (see  FIG. 2 ). The axles of the guide rollers  7  point radially away from the axis of rotational symmetry of the drum  2 . On the side of the guide rollers  7  facing away from the axis of rotational symmetry of the drum  2 , the axles of the guide rollers are held by guide-roller holders  8 . These guide-roller holders  8  are fixedly mounted on the frame  1 . The guide rollers  7  are mounted eccentrically on at least one side of the frame  1 , as a result of which the drum  2  is mounted without play in the frame  1 . 
         [0057]    Arranged on the side of the frame  1  lying opposite to the rockers  6  there is a V-belt  9 , which runs in a groove worked into the drum  2 . The V-belt  9  is driven by a drive roller  11 . It encircles the drum  2  and the drive roller  11  without crossing. The lower part of the V-belt  9  is pushed up, and thus tensioned, directly after the drive roller  11  by means of a tension roller  12 . Both the drive roller  11  and the tension roller  12  are mounted on the frame  1 . The axle of the drive roller passes through the frame  1  and is driven by a motor  13  on the other side of the frame  1 . 
         [0058]    On the side of the V-belt  9  facing away from the frame  1 , a slip ring  14  has been attached to the drum  2  in an interface provided therefor, said slip ring establishing the electrical contacts for the instruments and components that are attached to the drum  2  (not illustrated) via a brush (not illustrated) attached to the frame  1 . This contact to the slip ring  14  moreover enables precise positioning of the drum  2 . Appropriate slip ring systems are known and are offered by e.g. Schleifring, Fürstenfeldbruck, Germany. 
         [0059]      FIG. 2  shows a frontal view of the support system, according to the invention, for scanners. Here, the symmetric arrangement of the lower rollers  4  at angular coordinates 135° and 225° and the upper roller  5  at angular coordinate 0°, and also of the guide rollers  7  and the guide-roller holder  8  at angular coordinates 45°, 180° and 315° around the drum  2  are clearly visible. 
         [0060]      FIG. 3  shows an oblique view of the support system, according to the invention, for scanners. In contrast to  FIGS. 1 and 2 , this view shows the rear side of the support system. 
         [0061]    The two rockers  6  are mounted on the frame  1  and each hold two lower rollers  4 . (The lower rollers  4  are only visible from the other side; see  FIGS. 1 and 2 .) A housing  15  is attached to the frame  1  and houses the eccentrically mounted upper roller  5 . (The upper roller  5  is only visible from the other side; see  FIGS. 1 and 2 .) 
         [0062]    A hole pattern (not illustrated) is situated on the side of the drum  2  shown here and enables the instruments and components (not illustrated) to be attached to the drum  2 . 
         [0063]      FIG. 4  is an oblique view of a second support system, according to the invention, for a scanner. 
         [0064]    The illustrated support system once again comprises a frame  101 , which is formed from a steel plate  120  on which, on the base side, a support plate  120   a  that runs perpendicular to said plate is arranged. 
         [0065]    The frame  101  forms an opening, in which a substantially hollow-cylindrical drum  102  has space, with the axis of rotational symmetry thereof being perpendicular with respect to the plane of the frame  101 . The diameter of this drum  102  is approximately eight times greater than the length of the drum  102 . The drum  102  is forged without joints from heated and tempered steel C45 (pursuant to DIN EN 10027-1). A rail  103  with a rectangular cross section, which runs in the center of the lateral face of the drum  102 , encompasses the drum  102  in an annular manner. Together with the drum  102 , the rail  103  is forged from one part. The three free faces of the rail are induction hardened (58 (0/+4) HRC). The drum  102  is mounted in the frame  101  such that the annular rail  103  runs substantially in a central plane of the frame  101 . Here, on the external side (i.e. the side facing the frame  101 ) the annular rail  103  is borne by four rollers  104  lying therebelow, which are arranged in two pairs and mounted on the frame  101  on a support structure  121  attached to the frame  101  on both sides. The rollers  104  are either manufactured completely from through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1) or else they have bearing surfaces made of through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1). 
         [0066]    In a polar coordinate system, in which the angular coordinate starts at 0 degrees at the top-most point in the opening of the frame  101  and then rotates in the plane of the frame  101  in a clockwise direction, respectively one pair of the lower rollers  104  is mounted on the frame  101  at 135° and at 225°. The weight of the drum  102  is borne by these two pairs of lower rollers  104 . Both pairs of the lower rollers  104  are rotatably attached to a roller support  130  with the axles of the lower rollers  104  being parallel to the axis of rotational symmetry of the drum  102 . The roller support  130  can move, tangentially with respect to the drum  120 , on a linear guide  140 . It is described in detail below, in conjunction with  FIGS. 5-8 . 
         [0067]    So that the rail  103  of the drum  102  and the frame  101  remain in one plane, guide rollers  107  are attached to the frame  101 ; these guide rollers consist of through-hardened (59 (0/−1-4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1) or have at least bearing surfaces made of through-hardened ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1). These guide rollers  107  are respectively arranged in pairs, wherein, per pair, one guide roller  107  is attached on one side of the frame  101  and hence the rail  103  and the other guide roller  107  is attached on the other side of the frame  101  and hence the rail  103 , and run on the respective side face of the rail  103 . The mounts of the roller axles are attached to the steel plate  120 , the axles run radially inward. Overall, three pairs of guide rollers  107  are arranged symmetrically around the drum  102  at the angular coordinates 45°, 180° and 315°. The guide rollers  107  are mounted eccentrically on at least one side of the frame  101 , as a result of which the drum  102  is mounted without play in the frame  101 . The bearing surfaces for the rollers  104  formed on the rail  103  and the guide rollers  107  have been lubricated in order to reduce the noise development and the wear on the rollers. 
         [0068]    Arranged on one side of the frame  101  there is a V-belt  109 , which runs in a groove worked into the drum  102 . The V-belt  109  is driven by a drive roller  111 . It encircles the drum  102  and the drive roller  111  without crossing. The lower part of the V-belt  109  is pushed up, and thus tensioned, directly after the drive roller  111  by means of a tension roller (not illustrated) as known per se. The axle of the drive roller  111  is driven by a motor  113 . The motor  113 , the drive roller  111  and the tension roller  112  are mounted on a holding plate  116 , which is attached to the support structure  121  on the outside, as seen axially. 
         [0069]    A slip ring  114  has been attached to one side of the drum  102  in an interface provided therefor, said slip ring establishing the electrical contacts for the instruments and components that are attached to the drum  102  (not illustrated) via a brush  117  attached to the frame  101 . This contact to the slip ring  114  moreover enables precise positioning of the drum  102 . Appropriate slip ring systems are known and are offered by e.g. Schleifring, Fürstenfeldbruck, Germany. 
         [0070]      FIG. 5  is a detailed view, from a first side, of an installed roller support with two rollers.  FIG. 6  is a detailed view of the roller support from a second side.  FIG. 7  is an oblique view of the roller support and  FIG. 8  shows a cross section through the roller support. 
         [0071]    The roller support  130  comprises two roller bearings  131 ,  132 , in which respectively one roller  104  is mounted on one side. The mounting is in this case brought about by means of pretensioned angular ball bearings, as can be seen in e.g. EP 1 907 717 B1 (Güdel Group AG). The two roller bearings  131 ,  132  are housed in a common housing  133 . A groove  133   a  is formed on the underside of the housing  133 . A central piece  133   b  of the housing extends forward, parallel to the axles of the rollers  104 , with the front end of the central piece  133   b  projecting beyond the rollers  104 . A further groove  133   c  is formed on the underside of the front end that projects beyond the rollers. Bearing surfaces are formed in both grooves  133   a ,  133   c , and so the roller support  130  can slide on two rails  141 ,  142  of a linear guide  140 . Applied to the contact areas of the rails  141 ,  142  there advantageously is a damping plastic layer, e.g. made of ethylene chlorotrifluoroethylene (ECTFE), which is commercially available under the trademark Turcite®. 
         [0072]    The linear guide  140  comprises a base profile  143  to which the rails  141 ,  142  are screwed. In the outward direction, the base profile  143  extends upward at an angle of 45° with respect to the horizontal and is attached to the support structure  121  on both sides. 
         [0073]    The movement made possible by the linear guide  140  ensures that the weight of the drum  102  is distributed uniformly on all lower rollers  104 . Within the scope of operating the device, a path of approximately 5 mm is sufficient for the roller support  130 . 
         [0074]      FIG. 9  shows an oblique view of a third support system, according to the invention, for a scanner. In many respects, the illustrated support system corresponds to that according to the second embodiment illustrated in  FIGS. 4-8 ; the components with an identical design, such as the drive or the means for data transmission from the drum to the frame, have therefore no longer been illustrated. 
         [0075]    The illustrated support system once again comprises a frame  201 , which is formed from a steel plate  220 , on which, on the base side, a support plate  220   a  that runs perpendicular to said plate is arranged. The frame  201  forms an opening, in which a substantially hollow-cylindrical drum  202  has space, with the axis of rotational symmetry thereof being perpendicular with respect to the plane of the frame  201 . The diameter of this drum  202  is approximately eight times greater than the length of the drum  202 . The drum  202  is forged without joints from heated and tempered steel C45 (pursuant to DIN EN 10027-1). On the outside, the drum comprises a raceway  203  with a prism-shaped cross section, on which two bearing surfaces are formed which are respectively arranged at 45° to the rotational axis of the drum and hence include an angle of 90°. The bearing surfaces of the raceway  203  are induction hardened (58(0/+4) HRC). The drum  202  is mounted in the frame  201  such that the edge at which the two bearing surfaces meet runs substantially in a central plane of the frame  201 . Here, on the external side (i.e. the side facing the frame  201 ) the raceway  203  is borne by eight rollers  204  lying therebelow. Four of these rollers  204  are respectively rotatably mounted on a roller support  230 , with each of the two roller supports  230  respectively having two rollers  204  on each side of the central plane of the frame  201 . The rotary axles of the rollers are angled at 45° with respect to the rotational axis of the drum  202  and arranged such that they interact with the bearing surface of the respective side, i.e. two roller pairs are opposite to one another with rotary axles that are angled at 90° with respect to one another. 
         [0076]    The roller supports  230  are mounted on the frame  201  on a support structure  221  attached to the frame  201  on both sides. The rollers  204  are either manufactured completely from through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1) or else they have bearing surfaces made of through-hardened (59 (0/+4) HRC) ball-bearing steel (100Cr6 pursuant to DIN EN 10027-1). The outer surfaces of the rollers are ground like a ball such that differential slip is prevented in the region of the running contact. 
         [0077]    In a polar coordinate system, in which the angular coordinate starts at 0 degrees at the top-most point in the opening of the frame  201  and then rotates in the plane of the frame  201  in a clockwise direction, respectively one pair of the lower rollers  204  is mounted on the frame  201  at 135° and at 225°. The weight of the drum  202  is borne by these two pairs of lower rollers  204 . The roller support  230  can move, tangentially with respect to the drum  220 , on a linear guide  240 . It is described in detail below, in conjunction with  FIG. 11 . 
         [0078]    A third roller support  235  with four further rollers  204  is arranged at the top, at 0°. This roller support  235  also interacts with both bearing surfaces of the raceway  203 . It is described in detail in conjunction with  FIG. 10 . 
         [0079]    The rollers  204  assume the supporting function (in the case of the lower roller supports  230 ) and at the same time laterally guide the drum  202  as a result of their angled arrangement, i.e. hold it in the plane of the opening of the frame  201 . 
         [0080]    The bearing surfaces for the rollers  204  formed on the raceway  203  are lubricated in order to reduce the noise development and the wear on the rollers. 
         [0081]      FIG. 10  is a detailed view of an upper roller support  235  and  FIG. 11  is a detailed view of a lower roller support  230 , respectively in the installed state. 
         [0082]    The roller supports  230 ,  235  respectively comprise four roller bearings, in which respectively one roller  204  is mounted on one side. The mounting is in this case preferably brought about by means of pretensioned angular ball bearings, as can be seen in e.g. EP 1 907 717 B1 (Güdel Group AG). The four roller bearings are housed in a common housing  233 . 
         [0083]    Analogously to the roller supports as per the second embodiment, the lower roller supports  230  are also linearly moveable along a guide  240  running tangentially with respect to the drum  202 . Applied to the contact face between the guide  240  and the roller support  230  there advantageously is a damping plastic layer, e.g. made of ethylene chlorotrifluoroethylene (ECTFE), which is commercially available under the trademark Turcite®. The movement made possible by the linear guide  240  ensures that the weight of the drum  202  is distributed uniformly on all lower rollers  204 . Within the scope of operating the device, a path of approximately 5 mm is sufficient for the roller support  230 . 
         [0084]    The upper roller support  235  is mounted on the frame  201  via springs  236 . The springs  236  carry the roller support  235  and hence the rollers  204  onto the drum  202  and thereby ensure continuous contact between the bearing surfaces and the rollers  204 . As a result, diameter variations as a result of thermal influences can be absorbed. 
         [0085]    The invention is not restricted to the illustrated exemplary embodiments. Depending on the specific application, the edge of the drum between the instruments and components attached to the drum can for example have recesses, as a result of which the overall mass of the drum is reduced. This enables the use of a motor designed for less power and an accordingly less strong V-belt. 
         [0086]    Moreover, the V-belt can for example by replaced by a toothed belt or other types of driving belts. 
         [0087]    By way of example, depending on the specific application, it is also possible to vary the arrangement of the driving belt, the slip ring and the holes for attaching instruments and components on the drum. In doing so, driving belts, slip ring and also holes can be placed on the drum on one side of the frame or the other. 
         [0088]    Depending on the application of the support system, it is possible to modify the arrangement and number of rollers. Accordingly, the positions of the guide rollers can also be varied as required. 
         [0089]    In conclusion, it should be noted that the invention creates a support system for scanners, which enables short examination times but nevertheless has a cost-effective design.