Patent Publication Number: US-7896569-B2

Title: Joint arrangement for the connection of two segments of a patient bed

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicant hereby claims foreign priority benefits under U.S.C. §119 from German Patent Application No. 10 2005 054 175.5 filed on Nov. 14, 2005, the contents of which are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to a joint arrangement for the articulated connection of two segments of a patient bed, with two joint parts, each of which is connected rigidly to one of the segments and which are pivotable relative to one another about a common joint axis by means of a shaft journal, the joint parts carrying, in each case on at least one of their faces confronting one another axially, blocking faces intended for bearing against one another, and the joint parts being capable of being tensioned axially relative to one another by means of a tensioning mechanism. 
     BACKGROUND OF THE INVENTION 
     A joint arrangement of the abovementioned type is known, for example, from DE 102 53 906 A1. In the joint arrangement described there, the mutually confronting faces of the joint parts carry a toothing with a symmetrical tooth profile. This joint arrangement, as a rule, ensures a reliable hold in the respectively set position of the segments in relation to one another, as long as the tensioning mechanism is effective. In the known embodiment, the tensioning mechanism comprises an eccentric lever which is mounted pivotably on the shaft journal and which, when the eccentric lever is thrown, acts as a tie rod, by means of which the two joint parts are tensioned with their tooth profiles relative to one another. The oblique tooth flanks give rise, at least when the bed segments are subjected to load, to spreading forces which attempt to press the joint parts away from one another. If the tensioning mechanism is not tightened reliably or, for example, the eccentric lever is mistakenly adjusted in the opening direction, there is the risk that the loaded bed segment abruptly swings downwards. This risk is great particularly when the patient&#39;s entire weight bears on the respective bed segment. 
     SUMMARY OF THE INVENTION 
     The object on which the invention is based is to specify a joint arrangement of the type mentioned in the introduction which has a high load-bearing capacity and is functionally reliable. 
     This object is achieved, according to the invention, in that the blocking faces lie in each case at least approximately in a plane containing the joint axis. 
     In the joint arrangement according to the invention, the blocking faces are loaded perpendicularly to their plane, so that the load does not give rise to any spreading forces which attempt to press the joint parts away from one another. Even if, therefore, the tensioning mechanism is not tightened completely or has mistakenly been opened before the respective bed segment has been relieved of load, the blocking faces remain in engagement with one another, unchanged, so that a sudden downward swing of the loaded bed segment is avoided. Preferably, the joint parts carry, on their confronting faces one another, a toothing with a sawtooth profile, so that an adjustment of the bed segments in small steps about the axis of the shaft journal is possible. 
     So that the bed segments connected to one another via the joint arrangement according to the invention can also be separated from one another in a simple way, it is expedient if one of the joint parts is designed in a way known per se as a fork which can be slipped radially onto the shaft journal connected to the other joint part. In this case, to increase safety, the shaft journal carries a securing element which projects radially from it and which is dimensioned such that it closes, that is to say at least approximately fills, the fork aperture remaining after the fork has been pushed onto the shaft journal. 
     Closing the fork aperture prevents the situation where an operator, after slipping the fork onto the shaft journal, introduces his finger into the fork aperture and, during the pivoting of the bed segment connected to the fork, pinches his finger or fingers between a fork leg and a fixed part of the other bed segment. 
     Preferably, the securing element is mounted freely rotatably on the shaft journal, so that it is always set to the respective position of the fork aperture independently of the position of the shaft journal. 
     For additional securing, in the joint arrangement according to the invention, on one of the joint parts, a disengageable locking element may be arranged, which, in at least one predetermined pivoting position of the two joint parts, comes into effective engagement with the other joint part in each case, in order to prevent a relative movement of the joint parts at least in the direction of movement blocked by the blocking faces. This is advantageous, for example, for setting the bed segments in situations where one of the bed segments hangs approximately vertically downwards, whilst the bed segment connected via a joint arrangement according to the invention is again directed approximately horizontally, so that a patient can kneel on the latter bed element. Since, in this case, he rests virtually with his entire weight on the horizontal bed portion, it is necessary to ensure that this bed segment does not suddenly swing downwards, specifically not even when the tensioning mechanism of the joint arrangement is inadvertently opened. 
     Instead of the above-described tensioning mechanism with a tie rod and with an eccentric lever, the tensioning means may also comprise a screw grip which is in threaded engagement with the shaft journal, the two joint parts being tensioned relative to one another by the screw grip being screwed onto the shaft journal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention may be gathered from the following description which explains the invention by means of an exemplary embodiment, in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a diagrammatic side view of an operating table in a special position of the bed segments in order to explain the problem on which the invention is based, 
         FIG. 2  shows a perspective view of two bed segments connected to one another by means of a joint arrangement according to the invention, 
         FIG. 3  shows an enlarged part view of the joint parts of the bed segments to be connected to one another, 
         FIG. 4  shows a view, in the direction of the arrow A, of the fork-shaped joint part illustrated in  FIG. 3 , 
         FIG. 5  shows a perspective illustration of the bed segments illustrated in  FIG. 2 , in a position pivoted through 90° relative to one another, 
         FIG. 6  shows an enlarged view of a detail of the joint arrangement in the position of the bed segments in relation to one another, as illustrated in  FIG. 5 , 
         FIG. 7  shows a diagrammatic illustration, corresponding approximately to the view in  FIG. 3 , of the joint arrangement, in which the joint part comprising the shaft journal has been partially cut away, and 
         FIG. 8  shows a likewise partially cut away illustration of the joint arrangement in the position of the joint parts in relation to one another, as reproduced in  FIGS. 5 and 6 , and 
         FIG. 9  shows a section, containing the axis, through the joint arrangement. 
         FIG. 10  shows a section, containing the axis, through the joint arrangement of an embodiment of the invention having a screw grip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a highly diagrammatically illustrated operating table with a table column  10 , on the column head  12  of which is arranged a bed  14  which comprises a plurality of segments  16 ,  18 ,  20 ,  22  and  24  which are connected to one another and are adjustable in relation to one another via joints  26 ,  28 ,  30 ,  32 . The bed portions or segments  22  and  24  are set such that the segment  22  is directed almost vertically downwards and at its lower end carries the horizontally directed segment  24 . The patient  34  kneels on the latter in what is known as a rectal support. It is obvious that the patient&#39;s weight rests almost completely on the bed segment  24 . Particularly in such an instance, it is necessary to ensure that the joint  32  can be fixed in this position such that the bed segment  24  does not swing away downwards completely either gradually or suddenly, even if a tensioning mechanism closing the joint arrangement is inadvertently loosened or completely opened before the bed portion  24  is relieved of load. 
     The joint arrangement achieving this object, then, will be explained in more detail with reference to  FIGS. 2 to 8 . 
       FIG. 2  shows two bed segments  22  and  24  which serve as thigh and lower-leg supports and which are connected to one another by means of a joint arrangement  32  according to the invention. The joint arrangement  32  comprises a joint part  36  assigned to the bed segment  22  and a joint part  38  assigned to the bed portion  24  ( FIG. 3 ). The joint part  36  is formed on two mutually parallel end portions  39 ,  40  of a spar  42  of the bed portion  22 , the said end portions forming between them a gap  44  in which the joint part  38  of fork-shaped design on the bed segment  24  can be pushed. Through the two end portions  39 ,  40 , a shaft journal  46  extends, which is freely rotatable in the end portions  39  and  40  and which is designed as a tie rod and at one end carries a flange  48  with which it bears against the outside of a cylindrical thrust piece  49 . The thrust piece  49  is mounted axially displaceably in a bore of the end portion  40  and is secured against rotation with respect to the end portion  40  by means of an approximately radially projecting extension  51  which engages into a complementary clearance in the end portion  40  ( FIG. 6 ). The shaft journal  46  carries at its other end an eccentric lever  50  which is articulated on the shaft journal  46  about an axis  52  and acts on a thrust piece  54  which is mounted axially displaceable in the shaft journal  46  and is supported in a bore in the end portion  39  of the spar  42  on the latter. By the eccentric lever  50  being pivoted into the position illustrated in  FIG. 3 , the fork-shaped joint part  38  pushed in between the two end portions  39  and  40  can be tensioned between the inside of the end portion  40  of the spar  42  and the thrust piece  49 . Such an eccentric tensioning mechanism is known per se. 
     A toothed ring  56  which has a sawtooth profile is formed on the inner face of the thrust piece  49 . The fork-shaped joint part  38  carries, on its face confronting the thrust piece  49 , a toothed ring  58  with a complementary sawtooth profile. The steep short tooth flanks  60 ,  62  of the sawtooth profiles  56  and  58  lie in each case at least approximately in a plane containing the axis  64  of the joint arrangement  32 , that is to say in diametral planes of the joint arrangement  32 . When the two joint parts  36  and  38  are tensioned relative to one another via the tensioning mechanism  46 ,  50 ,  54 , the sawtooth profiles  56  and  58  coming into engagement with one another, the tooth flanks  60  and  62  bear against one another. If, then, for example, the bed segment  24  is loaded in the way illustrated in  FIG. 1 , this force acts in the circumferential direction perpendicularly to the tooth flanks  60 ,  62  acting as blocking faces against a rotational movement. As a result, even under high load, no spreading forces arise, with axial components which could press the toothed rings  56 ,  58  and consequently the joint parts  36 ,  38  apart from one another. Even if the eccentric lever were pivoted into its release position under the load on the bed segment  24 , as a rule, the two joint parts  38  and  36  would not be displaced spontaneously in the axial direction relative to one another, so that, even in the event of such maloperation, the bed segment  24  maintains its position in relation to the bed segment  22 . 
     To increase functional and operating reliability, a radial extension  66  is mounted freely rotatably on the shaft journal ( FIG. 8 ). This extension  66  is dimensioned such that it ends with a longer leg  68  of the two fork legs  68  and  70  of unequal length of the fork-shaped joint part  38 , as shown in  FIG. 8 . At the same time, the extension  66  completely fills the fork aperture remaining after the fork-shaped joint part  38  has been pushed onto the shaft journal  46 . When the fork-shaped joint part  38  is pushed onto the shaft journal  46 , the extension  66  is automatically set such that it assumes the position illustrated in  FIG. 8  in relation to the fork leg  68 . The extension  66  prevents the situation where any parts may engage into the fork aperture and obstruct the adjustment of the bed segments  22 ,  24  in relation to one another. The situation is also prevented where the operating personnel may pinch their fingers in the fork aperture. 
     Furthermore, on the spar  42 , carrying the joint part  36 , of the bed segment  22 , a locking button  72  also referred to as a disengageable locking element, is mounted pivotably about an axis  74 , the said locking button bearing with a locking nose  76  against the shorter fork leg  70  and being supported on the extension  66  when the bed portion  24  forms at least approximately a right angle with the bed portion  22 . The locking button  72  with the locking nose  76  prevents the situation where the bed segments  22  and  24  may be pivoted out of the angled position illustrated in  FIG. 8  into a stretched-out position, even if the eccentric lever  50  is pivoted into its opening position and the toothed profiles  56 ,  58  come out of engagement. Only when the locking button  72  is pivoted such that the locking nose  76  releases the extension  66  can the bed segment  24  be pivoted anti-clockwise in  FIG. 8 , the extension  66  and the fork leg  68  sliding under the locking nose  76 . This ensures further safety against an unintentional pivoting of the bed portions  22  and  24  in relation to one another. In order to facilitate the adjustment of the bed segments relative to one another and simplify operation, spring means may be provided between the joint parts, the said spring means pressing the joint parts apart as soon as the tensioning mechanism is opened and the bed segments are relieved of load. 
     While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention. 
     For example,  FIG. 10 , wherein like components have like numbers to those described with reference to  FIG. 9 , shows another embodiment of the present invention, in which the joint includes a modified shaft journal  78  having a threaded portion  80 . In the embodiment shown in  FIG. 10 , the joint parts are tensioned together by threading a screw grip  82  onto the threaded portion  80  of the modified shaft journal  78 .