Abstract:
An instrument comprises a headpiece at a proximal end, a shaft connected to said headpiece, said shaft can be deflected at least in a distal end area thereof. A deflection mechanism is provided for deflecting said shaft. Said deflection mechanism has control wires and a control element for controlling a deflection movement of said deflection mechanism. A lock is provided for locking said deflection mechanism. Said lock has a catch mechanism connected to said control element in such a way that said catch mechanism, without actuation, is automatically forced into a locking position and a movement of said control element first opens said catch mechanism and only then permits a deflection of said shaft. A release of said control element in any position of said deflection mechanism causes an enforced locking by said catch mechanism in said position.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an instrument with a proximal headpiece, with a shaft that can be deflected at least in the distal end area via a deflection mechanism, with a control element via which deflection movements of the shaft can be controlled by movement of control wires of the deflection mechanism, and with a lock for locking the deflection mechanism. 
     Such an instrument is known from DE 37 29 131 C1. 
     Such instruments are now in widespread use. 
     One field of use are medical instruments. Endoscopic instruments used for this purpose have a shaft portion that can be angled, at least at the distal end area. 
     It is in this way possible to introduce the shaft initially in an elongate state into a cavity of a living body. This can be done, for example, via a trocar or trocar sleeve inserted into a body or by way of natural orifices of the body, for example the mouth, the anus or urethra. The shaft can be deflected laterally within the cavity, such that, for example in the case of endoscopes, views can be gained to either side of the rectilinear direction. The shafts themselves can be of a rigid or flexible design, the crucial point being that the distal end area can be deflected. In the case of instruments serving purely as endoscopes, this provides an all-round view within the body cavity. If operating instruments, for example a needle holder, are mounted at the distal end, it is also possible to perform manipulations, e.g. suturing procedures, at locations within the cavity that cannot be reached by a rectilinear instrument. 
     A further field of use lies in particular in endoscopes used to inspect technical equipment. 
     One field of use is the inspection of structural parts that are difficult to access, e.g. the rear ends of the air vanes of aircraft turbines. By using deflectable endoscopes, such locations that are difficult to access can be inspected without dismantling the turbines. 
     Other fields of use are, for example, engine construction or bodywork construction, the latter case in particular requiring the inspection of cavity seals within hollow bodywork structures of complicated form. 
     Further technical fields of use are inspections of buildings or masonry. 
     The range of use of such instruments with deflectable shafts is becoming ever wider. 
     To permit the deflecting movement, a deflection mechanism is provided which is in most cases composed of control wires that are routed along the shaft and are connected to a control element at the headpiece. 
     For example, if the distal end is to be deflected in one plane away from the rectilinear orientation, two diametrically opposite control wires are provided. To permit deflection, one of the two control wires is now pulled in and the diametrically opposite control wire is pushed out, as a result of which the flexible end area of the shaft is curved or bent outwards in one plane. Such a control element can, for example, have a reel or roller on which the two control wires are secured. Rotation of the reel by the control element causes one control wire to be unwound in one direction, while at the same time the other control wire is reeled in. In the opposite direction of rotation, exactly the reverse procedure takes place. 
     It is thus possible for the deflectable area of the shaft to be deflected through almost 180° to both sides of the longitudinal axis. 
     In further developments, the deflection mechanism has two such pairs of control wires, which are arranged offset from each other by 90°, such that the deflectable area of the shaft can be deflected in two planes orthogonal to each other. It has become established practice to provide two control elements that operate independently of each other, as is known from DE 199 24 440 A1, for example. A combination of both movements permits the positioning of the distal end on a sphere surface. 
     It has now been observed in practical application that, after the deflection, a relatively strong restoring moment acts on the shaft, and this tends to bring the deflected shaft back to a more or less rectilinear state. In a bent flexible shaft, the outer envelope is compressed on one side and stretched like a rubber sheet on the other side. This results in relatively strong restoring forces. If the control wires are made of relatively stiff wire, restoring forces also occur upon deflection, that is to say bending, of the wires. 
     To avoid unwanted restoring of the deflected bent shaft, locks were developed that lock the deflected shaft against return from a defined position of deflection. 
     In addition to the deflection mechanism, it was thus also necessary to provide a locking mechanism via which the shaft can be locked against return from a respective position of deflection. 
     In DE 37 29 131 C1 mentioned at the outset, this is achieved by a combined brake lever and control lever. The lever, whose central rotation axle is connected to a reel on which the control wires can be wound and unwound, constitutes the control element of the deflection mechanism. If the shaft has been deflected into a defined position by means of the control lever, the lever has to be turned in another direction in order thereby to actuate a brake mechanism, which is designed to prevent restoring of the deflected area, i.e. is designed to block this movement. However, a certain amount of movement back and forwards for fine correction is still possible as before. 
     If the shaft is to be moved to another position of deflection or is to be made rectilinear again, the combined brake lever and control lever has to be moved in one direction to initially release the brake mechanism and then has to be moved in another direction in order to move the control wires of the deflection mechanism. 
     This is disadvantageous in the sense that different directions of movements and different manipulations have to be performed using one and the same control element, in order to be able to carry out the different procedures, namely, on the one hand, actuation of the deflection mechanism and, on the other hand, actuation of the brake mechanism. 
     In a starting position, the brake mechanism is free, and the deflection mechanism can now be actuated by the lever. The lever then has to be moved deliberately in another direction in order to activate the brake mechanism. 
     This is ergonomically unfavourable, requires a high level of attention and poses the danger of the deflected shaft moving out of position if the brake mechanism is not correctly actuated. 
     Moreover, the operator does not immediately know whether the lever is in a position in which it can be turned in order to actuate the deflection mechanism, or whether it is already in the brake function, since for this purpose it only has to be lifted a few millimeters from the rotation position. 
     This poses the problem that if pressure is inadvertently applied to the lever, the brake function is released and the deflected shaft moves. 
     This is fatal in the medical field in particular, for example if a surgical intervention is being performed with the deflected end. 
     It is, therefore, an object of the present invention to develop an instrument of the kind mentioned at the outset such that the control and in particular the locking and unlocking can be carried out safely, particularly using one hand. 
     SUMMARY OF THE INVENTION 
     According to the invention, this object is achieved by an instrument comprising a headpiece at a proximal end, a shaft connected to said headpiece, said shaft can be deflected at least in a distal end area thereof, a deflection mechanism for deflecting said shaft, said deflection mechanism having control wires and a control element for controlling a deflection movement of said deflection mechanism via said control wires, and a lock for locking said deflection mechanism, wherein said lock has a catch mechanism connected to said control element in such a way that said catch mechanism, without actuation of said control element, is automatically forced into a locking position, and wherein a movement of said control element first opens said catch mechanism and only then permits a deflection of said shaft, and wherein a release of said control element, in any position of said deflection mechanism, causes an enforced locking by said catch mechanism in said position. 
     These measures have a number of advantages. 
     By providing a catch mechanism, a mechanically simple and effective means is created for locking the shaft against undesired deflection movements. 
     This catch mechanism is brought positively, i.e. automatically, into the locking position when the control element is not moved or when it is released after a movement. The starting state or normal state is such that the catch mechanism is located in its locking position. 
     This has the advantage, for example for storage, for transport or for preparation of handling measures, that the shaft is in a clearly defined orientation from which it cannot move without the catch mechanism being released. It is thus possible to handle the flexible deflectable area, in this locked position, as a rigid shaft. 
     It is only when the control element is actuated, i.e. moved, that the catch mechanism initially opens and, upon further movement, a deflection of the shaft is possible via the deflection mechanism. When the control element is released, specifically in any position of the deflection mechanism, a direct and immediate movement into the locking position is enforced. The operator does not have to move the control element to some other position and instead simply releases it, as a result of which the catch mechanism immediately re-engages in the locking position. Basically, the operator has to move the control element only in one direction in order initially to release the catch mechanism and thereafter to effect the deflection movements. After it has been released, the catch mechanism is brought back immediately to its locking position, without further deflection movements being possible. 
     Therefore, the operator no longer has to know or ascertain whether the control element is in a state in which it has a locking action or permits a deflection movement, since it is always located automatically and positively in the locking state. Upon each movement of the control element, the locking action is always first released, and only then can the deflection movement take place, irrespective of whether this is a movement to deflect a rectilinear shaft or to bring a previously deflected shaft back to the rectilinear position. 
     In another embodiment of the invention, the catch mechanism has a row of teeth into which a movable detent can be introduced with a positive locking action, which detent can be moved out of the locking engagement by the control element. 
     This measure has the advantage that this positive control can be effected by mechanically simple but robust means. 
     In another embodiment of the invention, the detent is pretensioned resiliently in the direction of the row of teeth. 
     This measure has the advantage that the detent is permanently pretensioned in the direction of the locking engagement with the row of locking teeth and would therefore seek to move in this direction in whatever state. This can be achieved by the detent being subjected to the force of a spring, or by the detent itself being made of resilient material or being suitably shaped and inherently pretensioned. 
     This contributes to a simple mechanical structure and to consistently reliable handling. 
     In another embodiment of the invention, the row of teeth and the detent are shaped in such a way that a movement of the detent along the row is blocked, and only a movement of the detent out of the row permits a movement. 
     This measure has the advantage that, in the engaged state, a relative movement along the row of teeth is effectively blocked. It is only when the detent is moved out of the row of teeth that a movement of the deflection mechanism can take place. Particularly in connection with the aforementioned measure of the pretensioned detent, it is possible, with mechanically simple and robust structural parts, to create the conditions for ensuring, on the one hand, an engagement or locking that is automatically always closed when the detent is released, and for ensuring, on the other hand, that even very slight movements of the control element suffice to move the detent out of the locking engagement with the row of teeth. 
     In another embodiment of the invention, the teeth and the detent are shaped in such a way that the detent can be moved along the row of teeth when a predetermined counter-force is overcome. 
     By adaptation of the shape between teeth and detent and of the corresponding pressing force of the detent on the row of teeth, it is possible to ensure that the locking action along the row of teeth is subject to considerable forces and that the detent is disengaged only when a defined counter-force is overcome. It is then possible for the detent to run over the row of teeth. However, it is at all times ensured that, when the control element is released, the detent immediately and automatically engages in the next possible gap between two teeth and in this way once again provides the locking engagement. 
     In another embodiment of the invention, the teeth and the detent are shaped in such a way that a movement of the detent is blocked in one direction of said row of teeth but is possible in the opposite direction when said counter-force is overcome. 
     This possibility has the advantage of permitting particularly reliable deflection or control in two directions or opposite directions. 
     If a shaft is imagined in a rectilinear orientation, it can be deflected in one plane, for example to the left or to the right, using a pair of wires. If the shaft is to be deflected to the left, it is possible, by means of the aforementioned measure, to completely release the locking action in this direction. The detent can run over the row of teeth in the opposite direction. If each direction of movement is assigned a row of teeth, a detent can run over these in one direction, whereas, in the opposite direction, the detent first has to be lifted from the row. A second detent with opposite characteristics provides locking in the direction in which the other detent can travel over the teeth, and vice versa. 
     In another embodiment of the invention, the detent has an asymmetrical detent tooth which blocks the movement of the detent in one direction by positive locking and which can run over the row of teeth in the other direction, when said counter-force is overcome. 
     This measure has the advantage that the two-directional movement is made possible by structurally simple and mechanically robust measures. 
     In another embodiment of the invention, two detents are present, of which a first detent provides locking in a first direction along the row of teeth, and of which a second detent provides locking in a second direction opposite to the first direction, and the control element, upon movement in the first direction, releases the first detent from locking engagement and, upon movement in the second direction, releases the second detent from said locking engagement. 
     This measure has the advantage that, if the control element is not moved, both detents are in locking engagement and thus provide locking in both directions of movement. 
     If the control element is now moved in one direction, the detent that blocks this direction of movement is the one first brought out of the locking position. The other detent can run over the row of teeth when a certain pressing force is overcome. 
     If the control element is moved in the opposite direction, the detent blocking this direction is first of all lifted out of the row of teeth, such that the movement in this direction is made possible, in which case the other detent then runs over the row of teeth, again when a certain pressing force is overcome. 
     By structurally simple measures, it is here ensured that, in the direction blocked by a detent, it is this detent that is first lifted out of the locking engagement by the control element when the latter is moved in this direction, while the other detent can still run over the row of teeth in this direction when a certain pressing force is overcome. Thus, one of the detents is always connected to the row of teeth under a certain pressing force, so as to ensure that this detent comes into locking engagement directly after the control element is released. 
     In another embodiment of the invention, the row of teeth is designed as a pinion around which the detents are arranged as a pivotable single-arm lever. 
     This measure has the advantage of permitting a very compact structure. The pinion makes available an endless path of teeth, and suitably shaped detents or a suitable number of detents can then be arranged around the outer face of the pinion. 
     In another embodiment of the invention, the pinion has two rows of teeth, teeth of a first row can engage with a first detent and teeth of a second row can engage with a second detent. 
     These measures have several advantages. First, each row of teeth can be optimally adapted to the detent with which they engage. Mostly, the locking element of the detent is a detent tooth which acts with the teeth of the pinion in that the detent tooth locks absolutely in one turning direction of the pinion, but the detent tooth can run over the row of teeth in the opposite direction. Due to the fact that for each detent an individual row of teeth is provided, the geometry of the teeth of one row can be adapted optimally to the geometry of the detent tooth. As a result, the free motion when closing the catch mechanism can be diminished remarkably, since the row of teeth has to be adapted only to the detent tooth of one of the detents. Accordingly, the other row of teeth can be adapted optimally to the detent tooth of the other detent. As a result, in both turning directions of the pinion, only a very little free motion is present when closing the catch mechanism. This opens the possibility to arrange and to design the teeth asymmetrically, with the result that with small parts in one direction of turning of the pinion, an optimal catch action can be achieved, and in the opposite direction these teeth can be simply run over by the detent. 
     In a further embodiment of the invention, the pinion is assembled of two superposed pinion discs, each of which having a row of teeth which are directed oppositely to one another. 
     This measure has the advantage that both pinion discs can first be manufactured as individual parts and can then be assembled to a double-pinion with two rows of teeth. It is thereby possible to manufacture two identical pinion discs and to superpose it inversely. It is also possible to provide at one pinion disc a mounting feature via which it can be assembled with the other pinion in a predetermined orientation. This mounting feature may be a flange upstanding from one pinion disc, onto which flange the other pinion disc can be sliding. This opens different ways of mounting the pinion. 
     In another embodiment of the invention, the control element is designed as a rotary wheel, which is rotatable about the stationary pinion. 
     This measure has the advantage that the control element has a very favourable design from the ergonomic point of view and is easy to grip, and that the locking forces can be diverted or transferred to the instrument via the stationary pinion. 
     In another embodiment of the invention, a driver is arranged on the rotary wheel, which driver, in each position of rotation, engages with one of the detents and in so doing releases it from the locking engagement and keeps it released for as long as the rotary wheel exerts the force required for this on the detent. 
     This measure has the advantage that the deflection mechanism can be moved, or if appropriate can also be corrected, as long as this locking detent is maintained out of engagement by the rotary wheel. This state of course starts when the rotary wheel is gripped and moved. When a defined position of deflection of the shaft has been reached, the rotary wheel can continue to be held in the hand, that is to say counter to the restoring force of the deflected shaft, in order to optionally check the exact position of deflection. After the rotary wheel is released, the detent then immediately engages the row of teeth and blocks further movement. If a large deflection lever is chosen, that is to say long detents, and a small tooth engagement lever, the mechanism runs particularly smoothly. Jamming is also avoided. 
     In another embodiment of the invention, the released detent is pressed by the driver against an abutment on a driver disc, said driver disc being connected with a force fit to the deflection mechanism. 
     This measure has the advantage that the rotation movement of the rotary wheel is first used to disengage the locking detent from the locking engagement, without a deflection of the shaft thus already taking place. It is only after the driver presses the detent against an abutment on a driver disc that the latter is rotated, and the rotation movement is then transferred to the deflection mechanism. In this state, the operator can monitor or estimate the degree of deflection on the basis of the extent to which the rotary wheel is pivoted. He can then establish, if appropriate without direct visual control, how much the deflectable end has been deflected. 
     In another embodiment of the invention, two such deflection mechanisms are present in an instrument whose shaft can be deflected independently in two planes. 
     This measure has the advantage that in such devices, and in accordance with the underlying concept of the invention, these movements can be performed reliably and in an ergonomically simple way in both deflection planes. 
     In another embodiment of the invention concerning this latter embodiment, two rotary wheels are provided which are placed on each other and are held mechanically on each other, but which permit actuation of each of the rotary wheels independently of the other. 
     This measure has the advantage that the deflection movements to the left and right or upwards and downwards can be performed in the same way by the two rotary wheels. 
     It will be appreciated that the aforementioned features and those still to be explained below can be used not only in the cited combinations but also in other combinations or singly, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described and explained in greater detail below on the basis of a number of illustrative embodiments and with reference to the attached drawings, in which: 
         FIG. 1  shows a perspective view of an instrument with a shaft, the distal end area of which can be deflected, 
         FIG. 2  shows a cross section along the line II-II in  FIG. 1 , 
         FIG. 3  shows a greatly enlarged side view of a rotary wheel of the instrument from  FIG. 1 , 
         FIG. 4  shows a structural part, namely a detent, of the rotary wheel shown in  FIG. 3 , 
         FIG. 5  shows a greatly enlarged detail of a detent tooth of the detent, 
         FIG. 6  shows a cross-sectional detail of the detent from  FIG. 4 , of which the detent tooth is engaged between two teeth of a row of teeth, 
         FIG. 7  shows a view, comparable to  FIG. 6 , in which the detent tooth is running over one tooth of the row of teeth, 
         FIG. 8  shows a view, comparable to  FIG. 6 , of another illustrative embodiment of a detent tooth, 
         FIG. 9  shows a view, comparable to  FIGS. 6 and 8 , of another embodiment of a detent tooth, 
         FIG. 10  shows a view, comparable to  FIG. 3 , in a position in which the rotary wheel has been turned slightly in the clockwise direction and a detent has just lifted out of the row of teeth, 
         FIG. 11  shows a position, comparable to  FIGS. 3 and 10 , after the rotary wheel has been turned through 90° in the clockwise direction, 
         FIG. 12  shows a view, comparable to  FIG. 11 , after the rotary wheel has been released, 
         FIG. 13  shows a view, comparable to the view in  FIG. 10 , the rotary wheel having moved slightly in the anticlockwise direction from the view shown in  FIG. 12 , 
         FIG. 14  shows a side view of the rotary wheel from  FIG. 3 , partially in cross section, 
         FIG. 15  shows a cross-sectional view in which a further rotary wheel is placed onto the first rotary wheel from  FIG. 14 , 
         FIG. 16  shows a view, comparable to  FIG. 3 , of a further embodiment with a double-pinion, and 
         FIG. 17  shows a cross section along the line XVII-XVII in  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A flexible endoscope shown in  FIGS. 1 and 2  is designated in its entirety by reference number  10 . The flexible endoscope  10  is an instrument used in the medical field, for example for examining the digestive system of large animals such as cattle or horses via the rectum. 
     This instrument does not differ in principle from a flexible endoscope used in the technical sector, for example for inspecting the rear face of turbine blades of a turbine engine for an aircraft. 
     The endoscope  10  has a headpiece  12 . An eyepiece  14  protrudes from the proximal end of the headpiece  12 . A laterally protruding connector piece  16  serves for the attachment of a cable  18  that can contain leads for illumination, irrigation, insufflation, suction or the like. Another connector piece  20  extending more or less in the direction of the eyepiece  14  is provided to allow other instruments, for example forceps, snares or the like, to be inserted into the instrument. Two control elements  22  and  23  in the form of rotary wheels are arranged on the side of the headpiece  12  and can be used to adjust the viewing direction of the endoscope, as will be explained below. In the area of the headpiece  12 , there are also switches  24 ,  25 ,  26 , via which various functions can be controlled, for example suction, irrigation or the like. 
     An elongate, flexible shaft  30  continues from the headpiece  12  and, in the illustrative embodiment shown, has a length of approximately 1 m. The shaft  30  is produced from a flexible multi-layer structure, which permits curving and bending of the shaft  30 , as is shown in  FIG. 1 . A distal end area  32  has even greater flexibility than the shaft  30  in order to ensure that the distal end area  32  can also be deflected still further through more than 180° in a semicircle shape. This is possible in the first instance in one plane, as is shown in  FIG. 1 , that is to say in the plane of the drawing. In addition, the distal end area  32  can also be deflected perpendicularly with respect to the plane, that is to say upwards and downwards from this plane. Both deflection movements can be performed simultaneously, as a result of which the distal endpiece  34  (also called beak) moves on a surface of a sphere. 
     As can be seen from the cross-sectional view in  FIG. 2 , two pairs of control wires  36 ,  37  and  38 ,  39 , respectively, are arranged in the inside of the shaft  30 . These control wires are made of relatively stiff wire. The pair of control wires  36 ,  37  are connected to the control element  22  on the headpiece  12 . When the control element  22  is turned, for example in the clockwise direction, the control wire  36  is wound onto a roller operatively connected to the control element  22 , and at the same time the control wire  37  is unwound. Instead of a roller, a chain drive with a toothed wheel may also be present. In this way, an upward deflection of the distal end area  32  takes place. If the control element  22  is turned in the opposite direction, the control wire  37  is wound up and the control wire  36  is unwound, such that the distal end area  32  is then deflected downwards, as is indicated by an arrow. 
     The control wires  38  and  39  are correspondingly connected to the control element  23 . If the latter is turned in the clockwise direction, the wire  38  is wound up and the wire  39  is unwound and the distal end area  32  is deflected to the right, as is indicated in  FIG. 1  by solid lines. Accordingly, a rotation of the control element  23  in the opposite direction then causes a deflection to the left, as is shown by the broken lines. These structural parts thus constitute a deflection mechanism for the distal end area  32 . 
     To ensure that the deflected distal end area  32  remains in a defined position of deflection, a catch mechanism is provided by which the deflection mechanism is held in this position. 
     The control element  40  shown in  FIG. 3  corresponds to the first, inner control element  22  shown in  FIG. 1  and contains such a catch mechanism. 
     As can be seen from  FIG. 3 , the control element  40  is in the form of a rotary wheel  42 , with a plurality of finger recesses  44  provided on the outer face thereof. As can be also seen in particular from the partial cross-sectional view in  FIG. 14 , the control element  40  is composed of an annular body  46 . 
     This annular body  46  is pushed onto an assembly flange  52  of a driver disc  50  and is held firmly thereon by a securing means  53 . The driver disc  50  itself sits on a central shaft  48 . A rigid axle  54  extends through the shaft  48  and carries a pinion  56  which, in the view in  FIG. 14 , is arranged on the left-hand side, i.e. the side directed towards the headpiece  12  of the instrument  10 . The rigid axle  54  and thus also the pinion  56  secured thereon are likewise connected fixedly and immovably to the headpiece  12  of the instrument  10 . 
     Two detents  62  and  64  are mounted on that side of the driver disc  50  directed towards the headpiece  12 , as can be seen in particular from  FIG. 3 . Each detent  62  and  64  is made from a bent metal strip, and they are mounted pivotably on journals  66  and  68  protruding from the driver disc  50 . A detent tooth  70  protrudes from the detent  62 , and a detent tooth  72  protrudes in mirror image from the detent  64 , in each case in the direction of respective teeth  60 ,  60 ′ of the pinion  56 . 
     The detent  62  is shown in greater detail in  FIG. 4 . It will be seen from this that a spring  80  sits in a cutting (not described in any more detail here), one end of the spring  80  being received in the recess, and the other end bearing on a respective pin  74  or  76 , which likewise projects from the driver disc  54 . 
     By means of these springs  80 , the detents  62  and  64  are each pivoted about the journals  66  and  68 , respectively, such that the detent teeth  70 ,  72  thereof mesh in the pinion, that is to say between corresponding teeth  60 ,  60 ′ of the row of teeth. 
     It will be seen from the enlarged view in  FIG. 5  that the detent tooth  70  has two flanks  82 ,  84  of different steepness. The flank  82  is steeper than the flank  84  when seen in relation to the central longitudinal axis indicated by broken lines. 
     It will be seen from  FIG. 6  that the flanks  86  and  88  of the teeth  60  and  60 ′, respectively, correspond approximately to those of the flank  82 . 
     The view in  FIG. 6  corresponds to the situation of the detent  62  in  FIG. 3 . 
     Should the detent  62  be moved in the direction of the arrow as shown in  FIG. 6 , this movement is blocked by the flank  82  of the detent tooth  70  and by the corresponding flank  86  of the tooth  60 . 
       FIG. 7  shows that, in the opposite movement of the detent  62 , the shallower flank  84  can slide along the flank  88  of the tooth  60 ′, with the detent  62  being moved in the direction away from the teeth  60 ,  60 ′. 
     In other words, the detent  62  is able to run over the pinion  56  in the direction indicated by the downward arrow in  FIG. 7 . However, because of the force of the spring  80 , the detent  62  remains at all times in contact with the pinion  56 . When the detent tooth  70  has traveled over the tooth  60 ′, the detent tooth  70  engages back into the pinion, such that a situation such as the one shown in  FIG. 6  is reached once again. 
     From the sequence of  FIGS. 6 and 7 , it will be seen that a movement of the detent  62  along the row  58  of teeth  60 ,  60 ′ of the pinion  56  is blocked in one direction, whereas the detent can run freely over it in the opposite direction. 
     By virtue of the articulation on the journal  66 , the detent tooth  70  can be moved out of engagement in the direction of elevation of the teeth  60 ,  60 ′. 
       FIG. 8  shows a situation in which the geometry of the detent tooth  90  is configured such that its flanks are contoured in approximately the same way as the flanks  86  and  88  of the teeth  60  and  60 ′. In this configuration, a movement of the detent  62  is blocked in both directions along the row of teeth. 
     This blocking can be cancelled only if the detent  62  has first been completely lifted from the teeth  60  and  60 ′. 
       FIG. 9  shows a situation in which the detent tooth  92  is configured such that it has two relatively shallow flanks corresponding to the flank  84 . 
     In this case, the detent tooth  92  engages between the teeth  60  and  60 ′ of the pinion and initially blocks a lengthways movement between detent  62  and pinion. However, if the force acting on the detent  62  is so great that the pressing force is overcome by the spring  80 , the detent tooth  92  is able to run over the teeth  60 ,  60 ′ of the pinion  56  in both directions. 
     In all cases, by means of the corresponding detent tooth  70 ,  90  or  92  engaging between the teeth  60 ,  60 ′, a locking action is brought about between the detent  62  and the pinion  56 . 
     In all these locking states, the rotary wheel  40  cannot be turned about the pinion  56 . To do so, the corresponding detent tooth has to be moved out from between the teeth  60 ,  60 ′, as has been described above in connection with  FIGS. 6 ,  7 ,  8  and  9 . 
     When the above-described catch mechanism between detent  62  and pinion  56  is released, the rotary wheel  42  can be moved further and, in this way, the distal end area  32  can then be deflected via the deflection mechanism. 
     The embodiment of the catch mechanism discussed above in connection with  FIGS. 4 to 7 , and shown in principle in  FIG. 3 , will now be described in greater detail with reference to the sequence of  FIGS. 10 to 13 . 
       FIG. 3  shows a starting position in which the shaft  30  is in a rectilinear orientation. Both detents  62  and  64  are engaged in the pinion  56 . The two detents  62  and  64  curved in an arc shape extend, starting from the journals  66  and  68 , in an arc around both sides of the pinion  56  and, at the sides opposite the journals, they bear on both sides on a driver pin  78  that protrudes radially from the outside through the annular body  46  of the rotary wheel  42 . 
     Rotation in the clockwise direction is blocked because the steep flank  82  bears on the corresponding steep flank  86  of the tooth, as is indicated in  FIG. 6 . Because of the mirror-image configuration of the detent  64 , a movement in the anticlockwise direction is blocked because, in this direction of movement, the steeper flank of the detent tooth  72  is in locking engagement with the corresponding tooth of the pinion  56 . 
     Since both detents  62  and  64  are pretensioned by the corresponding springs  80  in the direction of the pinion  56 , this locking is maintained without external action. In other words, this state is automatically reached and maintained. 
     If the rotary wheel  42  is now turned slightly in the clockwise direction, as is shown in  FIG. 10 , the driver pin  78  moves the detent  62  away from the pinion  56 , as a result of which the locking engagement is cancelled. 
     The detent  62  can be pivoted radially outwards until it hits the pin  74  and closes there for a force fit between rotary wheel  40 , driver pin  78 , detent  62 , pin  74  and driver disc  50 . 
     From this point, the driver disc  50  thus also turns in the clockwise direction and then moves the control wires, as described above, and the distal end area of the shaft  30  is therefore deflected. 
     As can be seen from  FIG. 10 , the detent tooth  72  of the detent  64  runs in this direction with its shallow flank over the teeth  60 ,  60 ′ of the pinion  56 . The spring (not shown here) of the detent  64  presses the detent tooth  72  permanently into contact with the pinion. 
       FIG. 11  now shows a situation in which the rotary wheel  42  has been turned through approximately 90° in the clockwise direction. This rotation has caused a pivoting of the distal end area  32  through 90° from the rectilinear orientation. 
     If the rotary wheel  42  in the position shown in  FIG. 11  is now released, the force of the spring  80  presses the detent tooth  70  back into a free space between two teeth  60 ,  60 ′ of the pinion. This takes place immediately, without the rotary wheel  42  being able to turn further, since the engagement of the detent  64  with the pinion  56  already affords a preliminary locking in this position. If, in this state of rotation, the tips of the teeth of detent  62  and pinion  56  were to contact each other, a slight rotation movement can take place, but one that no longer has any effect on the deflection. Clamping is impossible, since the force of the detent  62  is not exactly radial and instead has a tangential component because of its articulation, such that a positive engagement of the detent  62  takes place. 
     This state is shown in  FIG. 12 . 
     It will be seen from this that the locking action provided by the catch mechanism is always present, and also maintained, when the rotary wheel  42  is released. This is independent of the position of rotation, for example in the starting position shown in  FIG. 3  or in the position of rotation shown in  FIG. 12 , where the distal end area  32  is deflected and considerable restoring forces act on the rotary wheel  42 . 
     If the deflected distal end area  32  is to be moved back into the rectilinear position, the rotary wheel  42  is turned anticlockwise from the position described in  FIG. 12 . 
     It will be seen from  FIG. 13  that the driver pin  78  then meets the other, opposite detent  64  and lifts the latter out of the locking engagement. In this position of rotation, the detent tooth  70  of the detent  62  can travel over the teeth of the pinion  56 . 
     When the end area  32  is then once again in a rectilinear orientation for example, that is to say the position shown in  FIG. 3  has been reached, the rotary wheel  42  can be released, and both detents  62  and  64  lock again. 
     A corresponding procedure occurs when, for example, the rotary wheel  42  is turned in the anticlockwise direction from the position shown in  FIG. 3 . The catch mechanism can thus be regarded as a catch mechanism that is self-unlocking in two directions. This procedure is ergonomic and also very simple to carry out from the tactile point of view, since the rotary wheel  42  can be gripped securely via the finger recesses  44 , and manipulations have to be performed only in one defined direction of rotation by turning the rotary wheel  42 , with the result that attention does not have to be paid as to whether a lock or catch is opened or closed, since it automatically closes when the rotary wheel  42  is released and is forcibly unlocked as soon as the rotary wheel  42  is turned. 
       FIG. 14  shows how the control element  40  described above is assembled. 
     The introduction described how, in many designs, a pivoting of the distal end area  32  of the shaft  30  in two different planes is desired. 
     For this purpose, as can be seen from  FIG. 15 , a second rotary wheel  100  corresponding to the rotary wheel  42  and approximately the mirror image thereof is mounted on the first control element  40  or rotary wheel  42 . To do so, as can be seen from  FIG. 14 , an assembly flange  94  protrudes from the rotary wheel  40 , and, as can be seen from  FIG. 15 , the rotary wheel  100  can be pushed onto this assembly flange  94  and held thereon. The rotary wheel  100  pushed on in this way is secured against falling off but can be rotated independently of the rotary wheel  42 . 
     In this case, the central rigid axle  54  extends so far that it reaches into the second rotary wheel  100 , such that the pinion  56 ′ of this rotary wheel can also be assembled thereon. Here too, a corresponding driver disc  50 ′ is once again provided, on which corresponding detents are assembled, of which the detent  64 ′ is shown here. 
     A driver pin  78 ′ is also provided here which extends between the two detents and, depending on the direction of rotation of the rotary wheel  100 , lifts them and thus cancels the locking action. The rotary wheel  100  is mounted on a further shaft  48 ′, such that this shaft  48 ′ is then rotated when the correspondingly deflected detent of the rotary wheel  100  is positively locked. It will be seen from  FIG. 15  that this shaft  48 ′ extends inside the shaft  48  of the rotary wheel  42  and runs over the outside of the rigid axle  54 . Thus, the other pair of control wires can be moved or controlled by the shaft  48 ′. 
     If the tooth geometry shown in  FIG. 9  is chosen, then, when one detent is lifted by the driver pin  78 , a corresponding pressing force of the other detent lying opposite has to be provided, such that this detent is in permanent contact with the pinion. 
     This structure can be chosen if the restoring forces by the deflected end area  32  are not very great. 
     Should these restoring forces be extremely great, or if extreme restoring forces act on the deflected distal end area because of manipulations, a tooth form such as the one in  FIG. 8  may be considered. 
     However, it is then necessary to ensure that both detents are lifted upon rotation of the rotary wheel. 
     Two detents have been described hitherto as separate structural parts. 
     They can be made from spring steel and, by suitable assembly, can be tensioned on the pinion. The springs  80  can then be omitted. 
     The two detents can be produced as a single structural part, connected to each other in the area of the journals  66  and  68 . 
     The underlying principle must always be satisfied, i.e. that the catch mechanism automatically closes after release of the rotary wheel but is freed with one and the same movement of the rotary wheel, as in the movement of the deflection mechanism. 
     From  FIGS. 16 and 17 , a further embodiment of a control element in the shape of a rotary wheel  102  is shown. For similar or identical structural parts, which have already been described in the previous embodiment, the identical reference numerals are used. 
     The rotary wheel  102  is designed, as described in connection with  FIG. 3 , as an annular body which is pushed onto a driver disc and held firmly thereon by securing means. A pinion  106  is mounted on a central shaft  48  and is assembled of two superposed pinion discs  108  and  110 . 
     The inner, or, in the view of  FIG. 16 , the lower first pinion disc  108 , is provided with an upstanding flange  112  onto which the second pinion disc  110  is pushed. 
     The first pinion disc  108  has along its outer circumferential edge a first row of teeth  114  which are shaped asymmetrically. 
     The second pinion disc  110  has at its outer circumferential edge a second row of teeth  110 , which are also asymmetrically, but they are oriented in the opposite direction. 
     The first row of teeth  114  of the first pinion disc  108  engages with a (not shown here) detent tooth of the first detent  62 . 
     The second row of teeth  116  of the second pinion disc  110  engage with the corresponding asymmetrical detent tooth  72  of the second detent  64 . 
     The two detents  62  and  64  are mounted on different levels for having its detent tooth engaging with its apparent row of teeth  114  and  116 , respectively. 
     As can be seen from  FIG. 16 , the asymmetrical detent tooth  72  of the second detent  64  is designed in that it can run over the teeth  116 , when viewed in clockwise direction, but catches counter-clockwise. A spring  109  provides that the second detent  64  is pushed against the teeth  116 . Correspondingly, the opposite first detent  62  is pushed by a corresponding spring  109 ′ against the row of teeth  114  arranged below in the view of  FIG. 16 . The second detent  64  catches in the opposite direction to the first detent  62 . 
     With that embodiment, the functional principle is the same as described before. If the rotary wheel  102  is, for example, turned counter-clockwise, the driver pin  28  lifts the second detent  64  and its detent tooth  72  out of the locking engagement of the second row of teeth  116  against the force of the spring  109 . This occurs almost without any free motion. Now, the rotary wheel  102  can be turned counter-clockwise. Thereby, the first detent  62  runs over the first row of teeth  114 , and that against the force of the spring  109 ′. 
     If the rotary wheel  102  is given free, the spring  109  pushes the detent tooth  72  of the second detent  64  into the next gap between two neighbored teeth  116 , and the mechanism is locked again. 
     The same applies for the opposite turning direction. In this case the driver pin  78  lifts the first detent  62  from the lower row of teeth  114  and the detent tooth  72  of the second detent runs over the teeth  116  of the second pinion disc  110 .