referring to fig1 an x - ray apparatus is shown generally at 10 . the x - ray apparatus 10 includes an x - ray tube housing assembly 12 , which is supported from an overhead support assembly 14 by a telescopic column 16 . the column 16 is comprised of a plurality of concentric tubular column sections 18 , 19 , 20 , 21 and 22 in nested and nesting relationship , and movable from a retracted position in which the sections are each substantially completely contained within the section 18 , to an extended position as shown in fig1 . each column section 18 - 22 has a cross - sectional shape as shown in fig2 . more particularly , each includes three flat surfaces indicated by the reference numeral of the section along with a designation a , b , c . each flat surface is spaced by three concave surfaces designated by the reference numeral of the section plus the designation d , e , f . the flat surfaces a , b , c of each section 18 - 22 serve to support guide plates or rollers , or both , for supporting the sections in a concentric relationship , for relative longitudinal movement . in the preferred embodiment , the flat sides that form any one of the sections 18 - 22 are equal in width and length , and are oriented at angles of 60 ° one to the other , equally spaced from each other , and thus lie in planes that define in cross - section an equilateral triangle . the widths of the sides of the different sections 18 - 22 are different , to facilitate nesting of the sections and to provide a clearance between the telescoped sections for guide plates 30 and roller assemblies 34 , which cooperate with each other to retain the sections in concentric relationship and to facilitate relative telescopic movement . three guide plates are carried by each section 18 - 21 , which are nesting sections . thus , guide plates 30a , b , c are supported on the inside surfaces of flat sides 18a , b , c ; guide plates 30d , e , f are supported on inside surfaces of flat sides 19a , b , c ; guide plates 30g , h , i are supported on inside surfaces of flat sides 20a , b , c ; and guide plates 30j , k , l are supported on inside surfaces of flat sides 21a , b , c . the guide plates 30 are located centrally of the widths of each flat side of the supporting section and extend the full length of the section . thus , the guide plates also lie in planes at 60 ° with respect to the others and are equally spaced one from the other . longitudinal side surfaces 36 , 37 of each guide plate serve as roller guides for the next adjacent nested section . three roller assemblies are carried by each section 19 - 22 , which are nested sections of the telescoped column . thus , roller assemblies 34a , b , c are supported on the outside surface of each flat side 19a , b , c of the section 19 and cooperate with the guide bars 30a , b , c of the nesting section 18 ; roller assemblies 34d , e , f are supported on the outside surface of flat sides 20a , b , c and cooperate with guide bars 30d , e , f ; roller assemblies 34g , h , i are supported on the outside surface of flat sides 21a , b , c and cooperate with guide bars 30g , h , i ; and roller assemblies 34j , k , l supported on the outside surface of flat sides 22a , b , c cooperate with guide bars 30j , k , l . the roller assemblies 34 , also shown in fig3 and 4 of the drawings , include a support plate 40 that is short relative to the length of each telescopic section , and each plate carries four rollers 41 , 42 , 43 , 44 spaced transversely and longitudinally of the respective sections . the plate 40 is carried parallel to the guide bar with which the rollers cooperate , and the transverse spacing of the rollers is equal to the width of the guide bar so that the rollers run along the opposite surfaces 36 , 37 of the guide bar . each assembly 34 is located adjacent the upper end of the telescopic section to which it is secured and stays within the adjacent nesting section of the column , even when the column is fully extended . the manner in which the guide bars 30 and roller supporting plates 40 are accurately located and secured to the sections of the column 10 is shown in fig5 to 7 with respect to the section 20 shown in fig3 . the manner in which the guide bars and roller supporting plates are secured to each section is substantially identical for all , except for the outer section 18 and the inner section 22 , which do not support both guide bars and roller assemblies . in those cases , it will be apparent that one or the other of the securing arrangements will be omitted . the flat side 20a of the telescopic section 20 and the attachment of parts thereto will be described , it being understood that the construction and arrangement of each of the other flat sides 20b , 20c is identical . circular apertures 50 are provided in the flat side 20a spaced along the length thereof and centered relative to the width . each aperture is counterbored at the outer surface of the flat side 20a . the depth of the counterbore can be varied to control the location of one or the other of the end surfaces of the plugs to accommodate for any lack of straightness in the section wall . plugs 52 , each with a cylindrical body and a flange 53 at one end , are located in the apertures 50 . the plug body has a central aperture 54 that is counterbored in the end surface that is flanged . the size of the cylindrical body of the plugs is selected so that it will be received within an apertures 50 with an interference fit , when the section and the plug are at the same temperature . also , the relative sizes of the plug body and aperture are selected so that , at a suitable temperature differential , the plug will fit within the aperture 50 with a slight clearance fit . because both the tubular section and the plugs are metal , they will respond dimensionally to a substantial extent in response to a temperature change . conveniently , the plugs are cooled in liquid nitrogen to reduce their dimensions relative to the size of the apertures 50 so they can be easily inserted into the apertures , but will return to a dimension that will cause them to be retained by friction when they reach the temperature of the section wall . an end face 56 of the plugs 52 opposite the end that is flanged serves as a mounting surface for the guide bars . the guide bars are initially , during assembly , located accurately with respect to the section so as to extend longitudinally in accurate alignment with the central axis thereof . this is conveniently done with a suitable jig or fixture and , with the guide bar properly aligned , it is secured to the plugs against the end faces 56 with screws 58 having associated lock washers , the screws fitting through the central passage 54 and being threadedly received in apertures 59 of the bar . to avoid any possibility of the guide bar being forced out of proper alignment due to clearances between the plug apertures and the screws , holes 60 are drilled through selected plugs 52 and through the bar 30 , and locating pins 62 are inserted to maintain the position of the guide bar 30 with respect to the section wall 20a . alternatively , separate plugs similar to the plugs 50 but without the central aperture for the screws can be utilized for receiving the locating pins . the plate 40 of the roller assembly 34 is secured to the outside surface of the flat side 20a by four machine screws 70 received in four plugs 72 , two of which are shown in fig7 . the plugs 72 are received in counterbored apertures 74 in the flat side 20a , with a friction fit the same as the plugs 52 are secured in the apertures 50 . each of the plugs 72 has a flange 74 at one end , received in the counterbore of the aperture , but the depth or height of the flange is greater than the depth of the counterbore . this spaces a top mounting surface 76 of the plug from the outer surface of the flat side 20a , to provide a mounting surface for the plates 40 , spacing them from the outer surface of the section wall . the depth of the counterbore can be controlled to assure that the surfaces 76 are accurately aligned in a common plane parallel to the plane of the guide bar with which it cooperates . the plate 40 is accurately located by pins 78 , 79 adjacent opposite ends , that extend through plugs . this is done by first locating the plate relative to the position of the guide bar 30 on the adjacent section with which it cooperates , e . g ., section 19 . the plate is then secured by the screws 70 . holes for the pins 78 , 79 are then drilled in the plugs and the pins inserted to retain the plate 40 in the proper position . in the arrangement shown , a separate plug 80 is provided for the pin 78 , and one of the plugs 52 used to secure the guide bar 30 receives the pin 79 . whether separate plugs or the plugs used to support the guide bar are used depends upon the convenience of the location relative to the mounting position of the plate 40 . the rollers 41 - 44 are supported on the plate 40 by screws 82 , spaced to straddle a guide bar and to run along the surfaces 36 , 37 . movement of the sections 19 - 22 of the telescopic column is controlled so that each nested section moves the same distance relative to its nesting section as the others . as a result , all sections extend progressively , each from the next simultaneously . the manner in which movement of the sections is effected and controlled is disclosed in the referenced support system patent . three pulleys 84 - 86 shown in fig2 secured at the top of the movable intermediate sections 19 - 21 carry cables ( not shown ) that interconnect the sections . a bundle 90 of four power cables , as best shown in fig1 and 8 , extends from the overhead support apparatus 14 to the housing assembly 12 at the end of the column 16 . pay out and take up of the cable bundle is conveniently , simply , and automatically controlled by a pulley wheel 92 carried by the first movable column section 19 . the pulley wheel is supported on a pulley shaft 94 connected to the wall portion 19e of the section 19 . the shaft extends through a longitudinal slot 96 ( fig8 ) in the wall portion 18e of the section 18 , and the pulley wheel is supported outside the stationary section 18 . with this arrangement , movement of the section 19 relative to the stationary section 18 moves the pulley wheel relative to the section 18 . the cable bundle 90 extends from the overhead support assembly 14 downward along the surface 18e of the section 18 , to the outside of and across the pulley 92 . the cable bundle is then looped back upward just above the lower end of the section 18 , is carried around the top of the pulley 92 and then extends downward from the pulley along the section 18 and subsequent sections . the pulley loop is confined by a cage 98 secured to the section 18 , and the cage and loop are then covered by a housing 99 ( fig1 ) with an opening at the bottom through which the cable extends . the cable bundle 90 is secured at the bottom edge of the third column section 20 in fixed relationship by a clamp 100 . with the above construction , when the sections 19 - 22 are extended , the pulley 92 will lower with the section 19 , paying out a length of cable equal to twice the distance that the section 19 travels , because two sides of the cable loop are shortened by the distance the pulley moves toward the bottom of the loop . because the cable is secured in fixed relationship to the third section 20 , the fixed point of the cable at the bracket 100 will travel twice as far as the pulley 92 , because it moves the combined distance of the sections 19 and 20 . as a result , the movement of the bracket 100 precisely accommodates the pay out of the cable from the loop and pulley 92 , resulting in a relatively taut or straight relationship of the cable bundle 90 along the column , between the bracket 100 and the housing 99 . upon retraction of the column sections , the pulley 92 moves upward relative to the section 18 , taking up the cable at a rate that accommodates the upward movement of the clamp 100 , maintaining the cable in a straight path along the second and third sections of the column . the variation in cable length along the fourth and fifth sections is accommodated by a cable loop adjacent the x - ray housing assembly 12 . this is acceptable because the change in length is occasioned only along two sections of the column and in fact is desirable to provide adequate cable for swinging the x - ray tube housing assembly about adjustment axes . from the above description it will be apparent that a telescopic column support apparatus has been provided in which sections of the column are conveniently fabricated and accurately aligned , and which provides a convenient and automatic cable take up and pay out arrangement . while the preferred embodiment of this invention has been described in detail , it will be understood that various modifications or alterations may be made therein without departing from the spirit and scope of the invention set forth in the appended claims .
an x - ray apparatus includes a telescopic column support with concentrically positioned tubular sections nested one within another . each of the sections except the innermost section has three guide bars triangularly spaced on the inner surface . each section except the outermost section has rollers on its outer surface cooperating with the adjacent guide bars of the surrounding section . the guide bars cooperate with the rollers in a generally circumferential direction rather than radially of the tubular members . mounting plugs held in apertures of the telescopic sections by an interference fit mount the guide bars and rollers . the plugs are initially insertable into the apertures with a clearance fit , when an appropriate temperature differential is established between the plugs and sections . a pulley wheel outside a fixed column section and carried by the first movable section supports a loop of control and power cables to take up and release the cables relative to a fixed location on a subsequent section , and at a rate equal to the change in length of the column , thereby avoiding slack in the cable during extension and retraction of the column .