fig1 shows a complete view of a patient support surface 10 which is connectable to the head 12 of a support column 14 of an examining table . the support surface 10 consists of a table plate 16 and a guide unit 18 , which includes an upper guide housing 20 and a lower guide housing 22 . the table plate 16 is slidably guided in the upper guide housing 20 in its longitudinal direction , as is illustrated by the two positions of the table plate 16 in fig1 . the lower guide housing 20 is slidably guided on the head of support column 12 in a non - illustrated way , so that the support surface 10 in its entirely is shiftable perpendicularly to the longitudinal direction of the table plate 16 . the table plate 16 has a thick middle section 24 with a trapezoidal cross section and two thin edge strips 26 along its longitudinal sides . the table plate is entirely , and indeed therefore in the area between both of the edge strips 26 , made without disturbing metal parts and therefore is artifact free in regard to penetration by rays . for example the table plate 16 is made of carbon fiber reinforced plastic . fig2 shows a side beam 28 of the upper guide housing 20 . at the ends of the side beam 28 are two roller blocks 30 which serve for guiding the table plate 16 in the longitudinal direction . between the two roller blocks 60 a brake unit 32 is arranged on one side , which brake unit is freely shiftable perpendicularly to the plane of the table plate 16 and which in the longitudinal direction abuts the beam 28 . also between the two roller blocks 30 is a drive unit 34 for shifting the table plate 16 . a roller block 30 is illustrated in more detail in fig3 and 4 . the roller block consists of a roller carrier 36 in which are supported the lower support rollers 38 and upper support rollers 40 . an edge strip 26 of the table plate 16 is positioned between the rollers 38 and 40 , so that the lower rollers 38 and the upper rollers 40 run on a lower guide surface 42 or an upper surface 44 , respectively , which are formed on the lower and upper side respectively of the edge strip 26 . for realizing a uniform load distribution , the roller carrier 36 is supported on the side beam 28 for pivotal movement about an axis 46 . during a longitudinal shifting of a the table plate 16 , the rollers 38 and 40 roll on the edge strip 26 of the table plate 16 . if the table plate bends because of the load , the roller block 30 adjusts itself by a pivotal movement about the axis 46 so that nearly similar forces are applied to the two roller pairs 38 , 40 . in this way the loading of the rollers is diminished as is also the loading of the upper surface of the table plate 16 , which leads to a reduction in the abrasion of the table plate 16 . for lateral guiding of the table plate 16 guide bars 48 are incorporated into the roller carrier 36 , which guide bars 48 inhibit a lateral deflection of the table plate relative to the upper guide housing 20 . fig5 shows the brake unit 32 in enlarged scale . the brake unit serves to avoid an unintentional movement of the table plate by way of external influences . the brake unit includes a frame 50 on which the rollers 52 are supported , by means of which rollers 52 the entire brake unit 32 runs on the edge strip 26 of the table plate 16 , that is on the upper guide surface 44 of a edge strip 26 . an upper brake shoe 54 is fastened to the frame 50 . on the upper brake shoe 54 are two levers 56 each of which is pivotally supported for movement about an associated axis 58 , which levers through further levers 60 carry a lower brake shoe 62 . if the two levers 56 are pivoted about their axes 58 , the distance between the two brake shoes 54 and 62 is changed . the pressing force for the brake shoes 54 and 62 is created through a spring 64 , which at one side abuts against a part 66 fixed to the frame and its other side abuts against a movable slide 68 , which in turn works on the lever 56 and biases the levers 56 in the direction of the arrow a in fig5 . the force of the spring 64 is amplified by the lever advantage of the lever . an electromagnet 70 serves for opening the brake and is fastened to the frame 50 , and with its armature 72 operates one of the levers 60 . if the electromagnet is energized , the armature 72 moves in the direction opposite to the arrow a of fig5 . the magnetic force overcomes the force of the spring 64 so that the slide 62 is moved to the right in fig5 and the brake is released . the actuation of the electromagnet 70 allows the table plate to be shifted , whereas in the non - activated condition of the electromagnet 70 , the brake holds the table plate 16 stationary . since because of the lever advantage for creating a large brake force , the relative stroke between the upper brake 54 and the lower brake shoe 62 is small and it must be avoided that in the case in of a bending of the table plate 16 the table plate does not rub on the brake shoes when the brake is released . for this reason the brake unit 32 is guided on the edge strip 26 of the table plate 16 by the rollers 52 , so that the brake shoes 54 and 62 independently of the bending of the table plate always have the same spacing from the surfaces of the plate . in the longitudinal direction the brake unit 32 abuts intermediate walls 74 of the side beam 28 . fig6 shows the drive unit 34 which serves for shifting the table plate in its longitudinal direction . it includes a drive roller 76 , which is driven by the a non - illustrated electric motor . the drive roller 76 stands in contact with two friction rollers 78 , which are positioned at the under guide surface 42 of the one edge strip 26 of the table plate 16 . the friction rollers 78 are each supported on a roller carrier 80 which is supported on a bolt 82 for free shifting movement within given limits , so that a change in the spacing between the drive roller 76 and the table plate 16 because of the loading of the support surface or because of rubbing due to the adjustability of the friction rollers 78 can be balanced . the required pressing force for the transmission of a moment by friction is in each case produced by a spring 84 , which abuts a block 86 holding the bolt 82 and biases the friction roller 78 through the roller carrier 80 against the drive roll 76 on one hand and on the other hand against the lower guide surface of the edge strip 26 . the brake unit 32 and the drive unit 34 can be provided in only of the side beams 28 or in both of the side beams of the upper guide housing 20 . fig7 and 8 show a second embodiment of the invention , wherein similar parts are provided with the same reference numerals . in the embodiment illustrated in fig7 and 8 the lower support rollers 38 extend over the entire width of the upper guide housing 20 and are supported in both of the side beams 28 . the table plate 16 lies on the lower guide rolls 38 with the underside of its middle section 24 forming the lower guide surface 88 . thereby the surface pressure on the rollers as well on the table plate is reduced . in the embodiment according fig7 and 8 , the lower support rollers 38 at the same time serve to provide a drive for a shifting of the table plate 16 . a motor 90 , through a toothed belt 92 and a belt pulley 94 , drives one of the support rollers 38 . a second belt pulley 96 coaxial to the belt pulley 94 transmits the relative movement of the one support roll 38 by means of a toothed belt 98 and belt pulley 100 to the other support roller 38 . it is thereby assured , that independently of the center of gravity of the table plate , with a patient lying on the table plate , a constant drive force is created . the lower support rollers 38 are coated with a layer 102 which has a high coefficient of friction , in order to create a sufficiently high drive force . the upper support rollers 40 , in the embodiment according to fig8 are positioned inclinedly , in order to reduce the height of the side beams 28 and therewith also the entire height of the examination table . the rollers 40 are in this embodiment made as track rollers which have a circumferential groove 104 so that they do not lie on the upper guide surface 44 of the edge strips 26 , but instead lie on the lateral edge surface 106 of the table plate 16 . thereby the rollers 40 in this embodiment in addition to opposing vertical forces also laterally guide the table plate 16 . in the embodiment according to fig8 a cushion 108 is also illustrated on the table plate 16 which cushion improves the lying comfort of the patient .
the invention relates to a bearing surface for a medical examining - table for carrying out roentgenolic examinations and surgical interventions during which radiological devices are used , comprising a table - top and a guide unit which can be coupled to a supporting column of the examining table . said guide unit has a first guide housing , in which the table - top is guided to that it can be displaced in the longitudinal direction . the table - top consists entirely of x - ray permeable material and has guide surfaces , which lie against guide elements in the guide housing .