DE102021121258B3 - Holding arm for a tripod of a surgical microscope, method for fixing the position of the holding arm and securing device for the holding arm - Google Patents

Abstract

The invention relates to a holding arm (100) for a stand (200) of a surgical microscope (202), with a proximal base part (102), with a distal receiving part (104), with a first arm extension (106) which has a first joint at one end (108) is articulated to the base part (102) and which is articulated at the other end to the receiving part (104) via a second articulation (110), with a second arm extension (112) which is articulated at one end via a third articulation (114) is articulated to the base part (102) and the other end is articulated to the receiving part (104) via a fourth joint (116), the joints (108, 110, 114, 116) having axes (118) aligned parallel to one another , With a device (120) for compensating for the weight force of a weight force acting on the distal receiving part (104), which comprises a spring (124) which in turn is supported on one of the arm extensions (106, 112) and is guided on this, and which has a traction medium el (122), which is connected at one end at least indirectly to one of the parts (102, 104) and at the other end at least indirectly to a free end of the spring (124), and to a side of the spring ( 124) present safety device (126), which is set up in the event of a traction mechanism tear to block at least one of the joints (108, 110, 114, 116) due to the action of the restoring force of the spring (124). The invention also relates to a method for fixing a holding arm (100) in position and a securing device (126) for such an arm.

Description

The invention relates to a holding arm for a stand of a surgical microscope, which has a proximal base part and a distal receiving part for receiving the surgical microscope. The holding arm comprises a device for compensating for the weight of a weight acting on the distal receiving part. The invention also relates to a method for fixing such a holding arm in position in the event of a traction mechanism tear. In addition, the invention relates to a safety device for such a holding arm.

A support arm of the type mentioned is for example from DE 197 11 572 A1 known. This has proven itself very well in practice. It forms part of a stand system that is placed and positioned appropriately over the object field to be observed, in particular the patient. During the operation, it may be necessary to move and reposition the microscope attached to the stand system in order to always ensure an optimal view of the object field. So that the movement forces required for the repositioning remain low, it is known to compensate for the weight forces that occur with the device for weight force compensation. However, there is a risk that the device for compensating for the weight force fails, which can lead to an unwanted, independent movement of the system and endanger the patient, the user or a third party.

For this reason it is, for example, from the CN 101 702 050 A It is known to design the traction mechanism of the device for compensating for weight forces redundantly, so that in the event of a tear in the primary traction mechanism, the safety traction mechanism, in particular the safety cable, which is slightly longer than the primary traction mechanism, becomes effective.

In the DE 41 11 408 A1 describes a support arm for computer devices, which is infinitely adjustable in height within a limited range and is designed to be self-locking in the set position.

In the DE 2 241 173 A describes a load balancing device comprising a frame formed by a parallelogram system. The load balancer includes safety brakes that limit the speed of movement of the parallelogram linkage and its lift arm in the event of an attached load unexpectedly dropping or if the control circuitry malfunctions when there is no load on the lift arm.

It is the object of the present invention to specify a holding arm for a tripod of a surgical microscope, a method for fixing the position of the holding arm in the event of a traction mechanism tear and a safety device for a holding arm which prevents the surgical microscope from lowering or falling down in the event of failure of the device for weight force compensation even better prevent or at least mitigate.

This object is achieved by a holding arm with the features of claim 1, by a method with the features of claim 14 and by a safety device with the features of claim 15. Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The holding arm according to the invention for a stand of a surgical microscope comprises a proximal base part and a distal receiving part. The first arm extension is articulated at one end to the base part via a first joint, and at the other end is articulated to the receiving part via a second joint. The second arm extension is articulated at one end to the base part via a third articulation, while at the other end it is articulated to the receiving part via a fourth articulation. The joints have axes aligned parallel to one another. The holding arm also includes a device for compensating for the weight of a weight acting on the distal receiving part, which includes a spring, which in turn is supported on one of the arm extensions and is guided on it, and which includes a traction mechanism which is connected at one end at least indirectly to one of the parts and the other end is at least indirectly connected to a free end of the spring. The holding arm has a safety device on a side of the spring facing away from the traction mechanism, which is set up to block at least one of the joints due to the action of the restoring force of the spring in the event of a traction mechanism tear.

The spring can be in the form of a spiral spring, a flat wire spring, a torsion spring, a set of disc springs or a gas pressure spring, as long as it is ensured that it exerts sufficient restoring force on the safety device in the event of a tearing of the traction mechanism and covers sufficient spring travel when relaxed to trigger it. The spiral spring itself can be designed as a tension spring or as a compression spring.

Due to the selected configuration of the two arm extensions on the holding arm and the resulting parallelogram kinematics, it is possible to compensate for the weight force if the device fails blocking one of the joints. As a result, all other joints are also indirectly blocked thereby, and movement of the holding arm is thus prevented. This reliably prevents the free end of the holding arm, on which the surgical microscope is typically attached, from sinking or falling down undesirably.

It is advantageous if a connecting piece is attached or formed on the end of the arm extension that guides the spring that faces the joint to be blocked, if this arm extension is connected in an articulated manner by means of the connecting piece to that part (receiving part or base part) on which the joint to be blocked is present if the safety device comprises a locking pin guided by the connecting piece, which is set up to be acted upon at least indirectly by the spring in the event of a rupture of the traction mechanism, and if the safety device comprises a locking pin receptacle which is designed to be non-rotatable in the event of a rupture of the traction mechanism, in particular form a non-positive and/or positive connection with the locking pin.

If the traction mechanism breaks, the energy stored in the spring of the device for weight force compensation (balancing system) is used to trigger or actuate the safety device. In this way, in the event of a traction mechanism tear, at least part of the energy stored in the spring is released, as a result of which it acts on the locking pin, which thus engages in the locking pin receptacle and thereby blocks the corresponding joint. In this way, all other joints of the parallelogram kinematics are also blocked, at least indirectly.

In this context, it is advantageous if a spring is used which, in the relaxed state, ie in the case of the state after a traction mechanism tear, provides a restoring force of at least 700 Newtons, preferably at least 1000 Newtons. In particular, with an acting restoring force of 1000 Newtons or more, it is reliably ensured that the locking pin is engaged in the locking pin receptacle and also remains engaged in it. In general, the following applies: The size of the spring force is selected depending on the torque that occurs or that is to be braked, with the structural design of the safety device also having an influence on the required restoring force.

The holding arm is particularly reliable when the arm extension includes a sleeve in which the spring is guided, and when the connecting piece is attached or designed in the form of a sleeve flange at one end of the sleeve that faces the part with the joint to be blocked .

In order to be able to ensure a stable stiffening of the joint in the event of a traction mechanism tear, it has proven useful if the locking pin is formed on its side facing the locking pin receptacle in a complementary manner with respect to the side of the locking pin receptacle facing the locking bolt. In this way, a frictional connection can also be supplemented by a form fit, which causes an even better stiffening of the joint in question and prevents the surgical microscope from sinking even more reliably.

In this context, it is also advantageous if the locking bolt is formed concavely on its side facing the locking bolt receptacle, and if the side of the locking bolt receptacle facing the locking bolt is formed convex.

It has proven to be advantageous if the center of curvature coincides with the pivot point (pivot point of the joint). In this way, it can be ensured in the most varied of pivoting positions of the holding arm that there is always contact between the locking pin and the locking pin receptacle that covers as much of the surface as possible when the safety device is triggered in the event of a traction mechanism tear.

In order to bring about an even better stiffening of the relevant joint, it makes sense if the surface of the locking bolt facing the locking bolt receptacle and/or the surface of the locking bolt receptacle facing the locking bolt is formed with teeth. The engagement of the teeth causes a further form-fitting coupling between the locking bolt and the locking bolt receptacle, it also being possible for locking teeth or sawtooth teeth to be present.

The locking pin can be realized, for example, as an impact wedge, namely when the locking pin tapers conically or wedge-shaped at least in sections along its longitudinal axis, and when the locking pin receptacle is set up to accommodate the locking pin tapering conically or wedge-shaped. In this way, due to the cone shape or the wedge shape, a frictional connection is realized between the wall of the locking pin receptacle and the surface of the locking pin. In the ideal case, a conical surface is in contact with a conical surface after a traction mechanism breaks. Preferably, the longitudinal axes of the present on the locking pin intersect truncated cone with the joint axis to be locked. The locking pin holder can be provided with a cone or a truncated cone on both sides in order to ensure that in any swiveling position of the holding arm in the event of a traction mechanism tear, the locking pin and the locking pin holder are in contact with as large an area as possible; at least, however, there is line contact on both sides. In particular, there is a flat contact when the locking pin has two semi-conical surfaces on the side and is ideally aligned for receiving the locking pin. If there is no ideal alignment, there is usually line contact.

It has proven to be advantageous if the locking bolt receptacle is assigned at least one latching recess into which a locking member can be engaged in the event of the traction mechanism tearing. The locking member is arranged between a wall of the locking bolt receptacle facing the locking bolt and a surface of the locking bolt facing the locking bolt receptacle. The locking member is, for example, a ball, a locking bolt or a locking cylinder. The use of a locking member has proven to be preferable because the relevant joint is reliably stiffened by a form fit realized in this way, so that due to the kinematics of the holding arm, sinking is avoided in the event of a tear in the traction mechanism.

In order to be able to reliably receive the locking member in a form-fitting manner in the most varied pivoting positions of the holding arm, there is preferably a chain of latching recesses on the locking pin receptacles. There can also be several locking elements and a number of chains of latching recesses adapted to the number of locking elements.

It has proven to be expedient for a reliable adjustment of the locking member in the event of a tear of the traction means that the wall of the locking bolt is provided with a locking member receptacle which has a wall running inclined with respect to the longitudinal axis of the bolt for guiding the locking member. This sloping wall pushes the locking member outwards in the event of a tearing of the traction mechanism, as a result of which it engages in the at least one latching recess of the locking pin receptacle and stiffens the joint in question.

There is the possibility that the locking member, in particular the ball, also only enters into a frictional connection in the event of a traction mechanism tear between the wall of the locking bolt and the wall of the locking bolt receptacle; In other words, the blocking member is jammed.

It is advantageous if the locking member is made of a material that is harder than the material of the locking pin and/or harder than the material of the locking pin receptacle. In the event of a traction mechanism tear, this leads to the locking element plastically deforming the material of the locking bolt and/or the material of the locking bolt receptacle and thus resulting in additional wedging and stiffening of the joint in question.

There is the possibility that the locking pin is formed with a recess extending in its longitudinal axis, which is designed to position the axis of the blocked joint between them in the event of a traction mechanism tear. In this way, the locking pin is moved even closer to that area in which the joint is present, so that the greatest possible force transmission for blocking the joint is available. The recess in the locking pin serves to enable the locking pin to penetrate sufficiently deep into the locking pin receptacle when the safety device is triggered, without colliding with the relevant axis of the joint.

However, there is also the possibility that the recess is provided with a suitable contour that acts on or clamps the axis of the joint itself in the event of a traction mechanism tear. It is also possible that, in the event of a traction mechanism tear, the axis of the joint radially widens the limbs forming the recess, so that the limbs are additionally clamped to the wall of the locking pin receptacle.

It has proven to be advantageous if the locking bolt is formed with two opposing contact surfaces that are inclined relative to its longitudinal axis, and if the locking bolt receptacle is set up to clamp the contact surfaces of the locking bolt between them in the event of a traction mechanism tear. The use of the contact surfaces offers reliable and operationally safe guidance of the locking pin when it engages in the locking pin receptacle.

It has proven to be advantageous if the locking pin receptacle interacting with the locking pin provides a conical surface which is formed to complement a conical contact surface, because then there is full-area contact when the two components are wedged, which provides reliable protection against further movement of the joint offers.

There is also the possibility if the locking bolt receptacle interacting with the locking bolt provides a conical surface, the wedge-shaped contact surfaces of the locking bolt being provided with edges which are in the case dig into the conical surface of the locking pin receptacle and offer even stronger locking.

In this context, there is also the possibility that the locking bolt receptacle is assigned brake inserts that act in the manner of brake shoes on the contact surfaces and thus on the locking bolt if the traction mechanism of the device for compensating for weight forces breaks off.

In general, it is advantageous if the surface finish of the locking pin and also the surface finish of the locking pin receptacle provide a suitable tribological pairing such that the largest possible coefficient of friction is effective between them. In this way, once a locking pin has been driven into the locking pin receptacle, it cannot easily be released again, which leads to an unintentional and undesired lowering of the surgical microscope mounted on the receiving part. However, primarily due to the increased friction, the torque/holding torque to be transmitted is suitably increased.

The locking pin provided with the contact surfaces can, in addition to the frictional connection, also enter into a form-fitting connection, for example when at least one of the contact surfaces is formed with teeth, in particular cutting teeth, or with notches. This offers even greater operational reliability of the safety device in the event of a traction mechanism tear.

Furthermore, it is advantageous if the material of the swivel joint and the material of the locking pin have a predetermined minimum hardness difference. For example, there is then the possibility that the locking pin will be shot into a softer part of the swivel joint by the moving tensioning means if the tensioning means tears off.

The advantages, advantageous configurations and effects explained in connection with the holding arm according to the invention apply in the same way to the method according to the invention for fixing the position of a holding arm in the event of a traction element tear.

This method is based on a holding arm mentioned above, which comprises a proximal base part, a distal receiving part, a first arm extension and a second arm extension. The first arm extension is articulated at one end to the base part via a first joint, and at the other end is articulated to the receiving part via a second joint. The second boom is articulated at one end to the base part via a third articulation, and at the other end is articulated to the receiving part via a fourth articulation. This holding arm has a device for compensating for the force of weight, which compensates for the force of the weight acting on the distal receiving part. This device for compensating for weight includes a spring connected to a traction device, with the energy stored in the spring being at least partially released and transferred to a safety device, which then stiffens one of the joints, if the traction device breaks.

In this way, in the event of damage, movement of the holding arm on the tripod is prevented and, at the same time, the energy released by the prestressed balancing system in the event of damage is used to trigger or actuate the safety device.

The spring of the device for weight force compensation is supported on one of the arm extensions, preferably on the first arm extension, and is guided on it. The traction mechanism is preferably at least indirectly connected at one end to one of the parts (base part or receiving part), preferably to the base part, and at the other end at least indirectly to a free end of the spring.

As a result of the restoring force of the spring acting in this way, either the locking pin can engage in a locking pin receptacle of the safety device assigned to the receiving part and stiffen one of the joints. Or it is possible that the restoring force of the spring triggers a mechanism of the safety device, particularly when the restoring force of the spring is not sufficient to actuate a locking pin or the like and/or when the resulting holding torque is not sufficient. Such a structure provides, for example, that the restoring force of the spring is used to actuate a firing pin of a cartridge; an "explosion" is triggered and actuates the locking bolt "like a bullet".

In normal operation, the locking bolt is sufficiently fixed in its position, it being ensured that this position is not left without the action of the spring of the device for compensating for the force of weight. Unintentional blocking of the joints without a traction mechanism tear is therefore impossible. A return spring acting in the longitudinal direction of the bolt can be used for this purpose. Furthermore, a resilient locking piece can be used, which fixes or holds the locking pin in its position. A radial orientation with respect to the longitudinal axis of the bolt oriented clamping of the locking pin is also possible.

In this context, there is, for example, the possibility that a retaining device, for example a retaining spring, is present, which ensures that the locking pin only leaves its position if the traction mechanism breaks. The force of the restraint device lags behind the restoring force of the spring of the balancing system.

The advantages, advantageous configurations and effects mentioned in connection with the holding arm according to the invention apply in the same way to the safety device according to the invention for such a arm. The safety device can also be retrofitted to existing holding arms.

The safety device according to the invention comprises a connecting piece that is set up to be attached to an end of the first arm extension that faces the receiving part. There is also a locking pin guided in the connecting piece. The safety device also includes a locking pin receptacle that is set up to be attached to an end of the receiving part that faces the first arm extension.

• 1 eine schematische Illustration eines Stativs mit einem daran angebrachten Operationsmikroskop,
• 2 eine Schnittansicht (von der Seite) durch einen Haltearm des Stativs aus 1 in einer Konfiguration, in welcher das Zugmittel des Balanciersystems intakt ist,
• 3 den Haltearm aus 2 in einer Konfiguration, in welcher das Zugmittel des Balanciersystems abgerissen ist,
• 4 das Detail IV aus 2 (in einer Seitenansicht),
• 5 das Detail aus V aus 3 (in einer Seitenansicht),
• 6 eine perspektivische Detaildarstellung (Teilschnitt) des Haltearms mit einer weiteren Sicherungseinrichtung, die eine oder mehrere Rastelemente in Form von Kugeln nutzt,
• 7 eine der 4 entsprechende Darstellung (eine Schnittansicht von oben) des Haltearms mit der Sicherungseinrichtung nach 6, bei der das Zugmittel noch intakt ist,
• 8 eine der 5 entsprechende Darstellung der Sicherungseinrichtung nach 6, bei der das Zugmittel abgerissen ist,
• 9 eine perspektivische Detaildarstellung (seitlicher Halbschnitt) des Haltearms mit einer nochmals weiteren Sicherungseinrichtung, bei der das Zugmittel noch intakt ist,
• 10 eine Schnittansicht von oben des Haltearms mit der Sicherungseinrichtung nach 9, bei der das Zugmittel noch intakt ist,
• 11 eine Schnittansicht von oben des Haltearms mit der Sicherungseinrichtung nach 9, bei der das Zugmittel abgerissen ist,
• 12 eine perspektivische Explosionsdarstellung der um Bremseinsätze ergänzten Sicherungseinrichtung nach den 9 bis 11,
• 12 eine weitere Gestaltung des Sperrbolzens in Form eines Klemmkeils,
• 14 eine nochmals weitere Gestaltung des Sperrbolzens in Form eines Klemmkeils,
• 15 eine nochmals weitere Gestaltung des Sperrbolzens in Form eines Klemmkeils,
• 16 eine perspektivische Explosionsdarstellung, bei der die Sicherungseinrichtung einen weichen Bremsklotz umfasst,
• 17 eine Schnittansicht (von der Seite) durch einen Haltearm des Stativs mit einer Sicherungseinrichtung nach 16,
• 18 eine mögliche Gestaltung des Sperrbolzens für die Sicherungseinrichtung nach 16,
• 19 eine weitere mögliche Gestaltung des Sperrbolzens für die Sicherungseinrichtung nach 16, und
• 20 eine nochmals weitere mögliche Gestaltung des Sperrbolzens für die Sicherungseinrichtung nach 16.

Further features, properties and advantages of the present invention are described in more detail below on the basis of embodiment variants with reference to the attached figures. All of the features described above and below are advantageous both individually and in any combination with one another. The embodiment variants described below merely represent examples which, however, do not limit the subject matter of the invention. show:

• 1 a schematic illustration of a tripod with a surgical microscope attached to it,
• 2 a sectional view (from the side) through a support arm of the tripod 1 in a configuration in which the traction mechanism of the balancing system is intact,
• 3 the holding arm 2 in a configuration in which the traction mechanism of the balancing system is torn off,
• 4 the detail IV 2 (in a side view),
• 5 the detail from V 3 (in a side view),
• 6 a detailed perspective view (partial section) of the holding arm with a further safety device that uses one or more locking elements in the form of balls,
• 7 one of the 4 corresponding representation (a sectional view from above) of the holding arm with the safety device 6 , in which the traction mechanism is still intact,
• 8th one of the 5 corresponding representation of the safety device 6 , in which the traction device is torn off,
• 9 a detailed perspective view (lateral half section) of the holding arm with yet another safety device in which the traction mechanism is still intact,
• 10 a sectional view from above of the holding arm with the safety device 9 , in which the traction mechanism is still intact,
• 11 a sectional view from above of the holding arm with the safety device 9 , in which the traction device is torn off,
• 12 a perspective exploded view of the safety device supplemented by brake inserts according to the 9 until 11 ,
• 12 another design of the locking pin in the form of a clamping wedge,
• 14 a further design of the locking bolt in the form of a clamping wedge,
• 15 a further design of the locking bolt in the form of a clamping wedge,
• 16 an exploded perspective view, in which the safety device comprises a soft brake pad,
• 17 a sectional view (from the side) through a holding arm of the tripod with a safety device 16 ,
• 18 a possible design of the locking pin for the safety device 16 ,
• 19 another possible design of the locking pin for the safety device 16 , and
• 20 another possible design of the locking pin for the safety device 16 .

In 1 a tripod 200 is shown on which a surgical microscope 202 is mounted. This tripod 200 includes a base 204 which is arranged vertically on a movable platform 208 provided with rollers 206 . With the base 204, a first support arm 210 is pivotally connected, this support arm 210 by a Axis can be pivoted, which corresponds to the longitudinal axis of the stand foot 204 SS. A retaining arm 100 is pivotally connected to the carrier arm 210 , the retaining arm 100 being pivotable with respect to the carrier arm 210 about an axis oriented parallel to the longitudinal axis of the base 204 . In this way, a SCARA tripod system (SCARA for "Selective Compliance Assembly Robot Arm") is implemented.

The holding arm 100 comprises a base part 102 which is pivotally connected to the carrier arm 210 . There is also a first arm extension 106 which is connected at one end via a first joint 108 to the base part 102 in an articulated manner. There is also a second arm extension 112 which is also connected in an articulated manner to the base part 102 at one end via a third joint 114 . The first arm extension 106 is connected at the other end in an articulated manner via a second joint 110 to a receiving part 104 on which the surgical microscope 202 can be mounted. The second arm extension 112 is also connected in an articulated manner to the receiving part 104 at the other end via a fourth joint 116 . The proximal base part 102, the first arm extension 106, the second arm extension 112 and the distal receiving part 104 result in parallelogram kinetics, which arise due to the mutually parallel axes 118 of the joints 108, 110, 114, 116. In addition, these axes 118 are oriented orthogonally with respect to the longitudinal axis of the base 204 . In this way, the holding arm 100 can be adjusted essentially vertically in accordance with the double arrow 212 . The units of the stand 200 for carrying the surgical microscope 202 can provide additional pivoting axes for the user, as in 1 is also indicated. They serve to position or manipulate the surgical microscope 202 around the three rotational degrees of freedom (ROTx, ROTy, ROTz).

In the sectional view of the support arm 100 according to 2 1 shows that the holding arm 100 is formed with a device 120 for compensating for the weight of a weight acting on the distal receiving part 104 . This has a spring 124 which is prestressed. The device 120 for compensating for the force of weight also includes a traction means 122, which in the present case is deflected around a deflection roller 166, so that the spring 124 is only tensioned axially and no transverse forces act on it.

In the present case, the traction means 122 is a toothed belt, with the deflection roller 166 being designed as a toothed belt pulley, because in this way there is a non-slip design of the device 120 for compensating for the force of weight. However, the traction means 122 can also be a chain, a rope, a toothless belt or the like. In these cases, the use of a chainring or a belt pulley or a cable pulley can be considered.

The traction means 122 is connected to the proximal base part 102 at an abutment point 154 . A joint piece 158 is present for this purpose, through which the traction means 122 is pivotally coupled to the abutment point 154 . In the present case, the abutment point 154 is realized by a nut, which can be adjusted up or down along a vertical spindle 156 depending on the weight acting on the receiving part 104 . The adjustability of the weight force compensation is necessary because different device configurations of the surgical microscope 202 and therefore different weight forces can be present on the receiving part 104 . By positioning the abutment point 154 along the spindle 156, the holding arm 100 can be balanced under a wide variety of weight forces.

While the traction means 122 is connected to the base part 102 at one end, it is connected at least indirectly to a free end of the prestressed spring 124 at the other end. In the present case, the spring 124 is guided on a movable tube 160 which in turn is arranged inside a sleeve 128 of the first arm extension 106 . The spring 124 is supported at one end on an annular shoulder 162 of the arm extension 106 or the sleeve 128. Opposite the spring 124 is assigned a flange 164 to which the traction means 122 is attached. The traction means 122 is guided through the movable tube 160 and acts indirectly on the free end of the spring 124, namely via the flange 164 supported by the spring end the deflection roller 166 is urged. It should be noted that the holding arm 100 can also be designed without the tube 160 and without the pressure roller 168 . In order to fix the holding arm 100 in its position, the deflection roller 166 is assigned an electromagnetic brake, which opens only when current is applied and blocks a rotation of the deflection roller when there is no current. This electromagnetic brake is thus designed to be “normally closed”.

The present invention deals with the problem that the traction means 122 could tear off due to continuous loads or due to fatigue. Such an error can lead to the holding arm 100 dropping, which is to be avoided. For this reason, the holding arm 100 has a safety device 126 which is present on a side of the spring 124 facing away from the traction mechanism 122 . The security device 126 is set up to block at least one of the joints 108, 110, 114, 116 due to the action of the restoring force of the spring 124 in the event of a traction mechanism tear. It is sufficient if only one of the joints 108, 110, 114, 116 is stiffened, since the movement of the other joints is then also inhibited. For this reason, an unintentional lowering of the holding arm 100 is excluded.

While the traction mechanism 122 of the holding arm 100 in 2 is still intact 3 the situation in which the traction means 122 is torn off. The safety device 126 comprises a connecting piece 130 assigned to the first arm extension 106, in particular the sleeve 128, a locking pin 132 being guided in this connecting piece 130. The locking pin 132 is set up to be acted upon at least indirectly by the spring 124 in the event of a tearing of the traction mechanism. The safety device 126 also includes a locking pin receptacle 134 assigned to the receiving part 104, which is set up to form a non-rotatable, in particular a non-positive and/or positive connection with the locking pin 132 in the event of a traction mechanism tear. In this way, the movement of the second joint 110 between the first arm extension 106 and the receiving part 104 is blocked in the present case and thus also inhibits the movement of all other joints 108, 114, 116. This stiffens the entire holding arm 100 and prevents or at least slowed down.

Out of 4 who made the configuration 2 shows in detail, it can be seen that the connecting piece 130 is attached in the form of a sleeve flange to the end of the sleeve 128 facing the receiving part 104 . The locking pin 132 is mounted in this sleeve flange so that, in the event of a traction mechanism tear, it can be acted upon by the spring 124 or by the flange 164 on its surface facing away from the receiving part 104 . The flange 164 can additionally be provided with a stamp in order to ensure an optimal transmission of the spring force to the locking pin 132 . It can be seen that the side of the locking pin 132 facing the locking pin receptacle 134 has a complementary shape with respect to the side of the locking pin receptacle 134 facing the locking pin 132 . In other words, the configuration of one of the locking bolts 132 and the locking bolt receptacle 134 is shaped negatively with respect to the other of the locking bolt 132 and the locking bolt receptacle 134 . In the design according to 4 and 5 the locking pin 132 is formed concave on its side facing the locking pin receptacle 134, the side of the locking pin receptacle 134 facing the locking pin 132 being formed convex. A frictional connection between the first carrier arm 106 and the receiving part 104 can thus be reliably implemented in order to stiffen the joint 110 . In order to further increase the strength of the stiffening, in addition to a frictional connection, a positive connection can also be implemented, for which purpose it is proposed to form both the locking pin 132 and the locking pin receptacle 134 with teeth 136, in particular with locking teeth. While in the untriggered state according to 4 of the safety device 126 there is still an air gap 152 between the locking bolt 132 and the locking bolt receptacle 134 is in the triggered state according to FIG 5 this air gap 152 no longer exists; the two components form an interlocking engagement.

In the 6 until 8th a somewhat different design of the safety device 126 is shown, in which the locking bolt 132 is formed to taper conically at least in sections along its longitudinal axis, and in which the locking bolt receptacle 134 is set up to accommodate the conically tapering locking bolt 132. On its surface 142 facing the locking bolt receptacle 134 , the locking bolt 132 has a locking element receptacle 170 in order to be able to position a locking element, in particular in the form of a ball 138 , between the locking bolt 132 and the locking bolt receptacle 134 . Instead of a ball, for example, a locking bolt or a locking cylinder can also be used. How out 6 results, the locking pin receptacle 134 has at least one locking recess 172 which is set up to accommodate the locking member, in particular the ball 138 in the event of a traction mechanism tear. In order to enable this "picking up" in the most varied pivoting positions of the holding arm 100, there is a chain of latching recesses 172 on the locking pin receptacle. There can also be several locking elements and a number of chains of latching recesses 172 adapted to the number of locking elements. In the event that the traction mechanism 122 breaks, a form fit is brought about by the ball 138 moving into the latching recess 172 . This can be done using the 7 and 8th understand more closely. The ball sits in 7 still in the locking member receptacle 170 of the locking pin 132; the safety device 126 is not triggered. If the safety device 126 is then triggered, the ball 138 is pushed outwards by the wall of the locking member receptacle 170 that runs inclined with respect to the longitudinal axis of the bolt, as a result of which the ball 138 engages in the latching recess 172 of the locking bolt receptacle 134 and latches there in a form-fitting manner; this situation is in 8th to recognize.

There is the alternative or supplementary possibility that the ball 138 is formed from a material that is harder than the material of the locking pin 132 and/or harder than the material of the locking bolt receptacle 134. In this way, the ball 138 can penetrate the material of the locking pin 132 and/or the material of the locking pin receptacle 134 in the event of a tear in the traction mechanism 122 and thus deform it plastically in order to achieve additional securing of the joint.

A further configuration of the safety device 126 is shown in the perspective detailed view 9 shown. Here, the locking pin 132 is formed with a recess 144 extending in its longitudinal axis, which in turn is designed to position the axis 118 of the blocked joint 110 between itself in the event of a traction mechanism tear. The recess 144 in the locking pin 132 serves to ensure that the locking pin 132 can penetrate sufficiently deeply into the locking pin receptacle 134 when the safety device 126 is triggered without colliding with the relevant axis 118 of the joint 110 .

the 10 and 11 FIG. 12 shows plan views of the securing device 126. FIG 9 , whereby 10 the untriggered state and 11 show the triggered state of the safety device 126 in the event of a traction mechanism tear. These plan views show that the locking pin 132 shown is also wedge-shaped with two opposing contact surfaces 146 that are inclined relative to its longitudinal axis, and that the locking bolt receptacle 134 is designed to close the contact surfaces 146 of the locking bolt 132 between them in the event of a traction mechanism tear jam. The surface of the locking pin receptacle 134 that interacts with the contact surface 146 of the locking pin 132 is preferably formed in the shape of a (partial) cone or (partial) truncated cone. In the present case, there is a cone or a truncated cone on both sides of locking pin receptacle 134, the longitudinal axis of which is oriented parallel, in particular coaxially, with respect to axis 118 of joint 110 to be locked directly, so that locking pin 132 can rest securely in the Locking pin receptacle 134 is guaranteed in the event of a traction mechanism tear. The cone is formed as flat as possible, for example with a cone angle of 170 degrees. In an analogous manner, the locking pin 132 can then also be provided with a slight inclination or a small cone angle, for example of 10 degrees. The locking pin 132 can be wedge-shaped with flat surfaces, so that in the event of a jam with an identical wedge/cone angle, there is line contact present, whereby these “lines” can also cut into the material of the locking pin receptacle 134. There is the possibility of forming the locking pin 132 with a corresponding negated/complementary semi-conical surface, so that in the case of jamming there is surface contact with an identical cone angle.

The jamming of the locking bolt 132 - formed as an impact wedge in this design - is illustrated by the circular detailed views, in which in 10 there is still an air gap 152, with in 11 this air gap 152 is no longer present due to the action of the spring force of the spring 124 . When using such contact surfaces 146, which are driven into the locking bolt receptacle 134 in the event of a traction mechanism tear, it has proven to be useful if the surfaces of the locking bolt 132 and/or the locking bolt receptacle 134 are coated with friction-increasing substances or there is a corresponding tribological material pairing that leads to increased friction.

This is also the case, for example, in the design of the safety device 126 12 so realized, in which the locking pin receptacle 134, which is formed in one piece with the receiving part 104, additional brake inserts 148 are associated to increase the friction. In this embodiment, the brake inserts 148 interact with the contact surfaces 146 of the locking pin 132 in the event of a traction mechanism tear.

In order to provide an even greater force for stiffening one of the joints 108, 110, 114, 116 in the event of a tear in the traction mechanism 122, in addition to the mere possibility of a frictional connection, the addition of a force and/or a positive connection is also possible. So shows 13 For example, the possibility of forming the contact surfaces 146 with a toothing 150, the design according to 13 includes a large number of teeth. In 14 a toothing 150 is present, which provides a smaller number of individual teeth on the contact surface 146, with the locking pin 132 after 15 on its contact surface 146 only provides a toothing 150 with a single tooth. The number of teeth is dependent on the design of the holding arm 100 and the weight forces acting on it. The teeth of the toothing 150 are suitable in order to "dig" or "bite" into the material of the locking pin receptacle 134 - under plastic deformation. Instead of teeth, notches can also be used, which also have sharp edges for “digging in” or “biting” into the material of the locking pin receptacle 134 or the brake inserts 146 in the event of a traction mechanism tear.

In the 16 Another design of the locking pin receptacle 134 is shown, which consists of a—soft—brake pad 174 is formed. It has recesses or openings running parallel to the axis of the joint so that it has the necessary deformability. The number of recesses is adapted to the forces acting when the safety device 126 is triggered. The locking pin 132 itself is in turn formed with teeth 136 which cut into the brake block 174 in the event of a traction mechanism tear and are secured in position there; similar to a saw blade stop on a circular saw.

17 shows the installation situation of the safety device 126 in the holding arm 100, the locking pin 132 in the non-triggered state being positioned at a small distance from the locking pin receptacle 134, and therefore the brake block 174, so that the joint 110 is movable. The brake block 174 and the locking bolt 132 are in turn formed with curved surfaces which are adapted to one another and whose center point in turn coincides with the joint axis 118 . In this way, it is ensured in every pivoted position of the holding arm 100 that the locking pin 132 can engage in the brake block 174 over a large area if the traction means 122 should tear off.

In 18 It can be seen that the toothing 136 of the locking pin 132 is formed with a small number of teeth, with three of the teeth being shown here. However, a different number is possible.

In 19 it can be seen that the toothing 136 of the locking pin 132 is formed with a larger number of teeth than the small number. The variant after 20 13 then shows a surface of the locking bolt 132 with a plurality of points 176 (“spikes”) which are driven into the material of the brake block 174 in the event of a traction mechanism tear.

In all of the configurations of the present invention, if the traction mechanism 122 breaks, the potential energy stored in the spring 124 is at least partially released and transferred to the locking pin 132 of the safety device 126 . The restoring force of the spring 124 acting on the locking pin 132 causes the locking pin 132 to engage in the locking pin receptacle 134 of the safety device 126 associated with the receiving part 104, as a result of which one of the joints 108, 110, 114, 116 is stiffened or at least made more difficult to move. The result of this is that all other joints 108, 110, 114, 116 are also inhibited with regard to their movement and thus an undesired sinking or falling of a surgical microscope 202 attached to the holding arm 100 is avoided or greatly slowed down.

Reference List

100

holding arm

102

base part

104

recording part

106

first arm extension

108

first joint

110

second joint

112

second arm extension

114

third joint

116

fourth joint

118

axis (joints)

120

Device for weight compensation

122

traction means

124

Feather

126

security device

128

sleeve

130

connector

132

Locking pin (arm extension)

134

Locking bolt mount (mounting part)

136

gearing

138

locking member

140

wall (locking pin mount)

142

surface (locking pin)

144

recess (locking pin)

146

contact surface (locking pin)

148

Brake insert (locking pin mount)

150

toothing

152

air gap

154

abutment point

156

spindle

158

joint piece

160

tube (movable)

162

ring shoulder

164

flange

166

pulley

168

pinch roller

170

Locking link mount (locking pin)

172

Locking recess (locking pin mount)

174

brake pad

176

sharpen

200

tripod

202

surgical microscope

204

stand

206

roll

208

platform

210

carrier arm

212

Double arrow (adjusting movement of the holding arm)

Claims (15)

Holding arm (100) for a tripod (200) of a surgical microscope (202), with a proximal base part (102), with a distal receiving part (104), with a first arm extension (106) which is articulated at one end via a first joint (108) to the base part (102) and which is articulated at the other end via a second joint (110) to the receiving part (104), with a second arm extension (112), which is articulated at one end to the base part (102) via a third joint (114) and the other end is articulated to the receiving part (104) via a fourth joint (116), the joints (108, 110, 114, 116) have axes (118) aligned parallel to one another, with a device (120) for weight force compensation of a weight force acting on the distal receiving part (104), which comprises a spring (124) which in turn is supported on one of the arm extensions (106, 112) and is guided on it, and which has a traction means ( 122) which is connected at one end at least indirectly to one of the parts (102, 104) and at the other end at least indirectly to a free end of the spring (124), and with a safety device (126) on a side of the spring (124) facing away from the traction mechanism (122), which is set up in the event of a traction mechanism tear, at least one of the joints (108, 110, 114, 116) due to the action of the restoring force of the to block the spring (124). Holding arm (100) according to claim 1 , characterized in that at the joint (108, 110, 114, 116) to be blocked facing the end of the spring (124) guiding arm extension (106, 112) a connecting piece (130) is attached or formed such that this arm extension (106, 112) is connected in an articulated manner by means of the connecting piece (130) to that part (102, 104) on which the joint (108, 110, 114, 116) to be blocked is present, that the safety device (126) has one of the connecting piece (130) guided locking bolt (132), which is set up to be acted upon at least indirectly by the spring (124) in the event of a rupture of the traction mechanism, and that the safety device (126) comprises a locking bolt receptacle (134) that is set up to be one in the event of a rupture of the traction mechanism to form a non-rotatable, in particular a non-positive and/or positive connection with the locking pin (132). Holding arm (100) according to claim 2 , characterized in that the arm extension (106, 112) comprises a sleeve (128) in which the spring (124) is guided, and that the connecting piece (130) in the form of a sleeve flange is attached to one end of the sleeve (128) or is formed which faces that part (102, 104) with the joint (108, 110, 114, 116) to be blocked. Holding arm (100) according to claim 2 or 3 , characterized in that the locking pin (132) is shaped on its side facing the locking pin receptacle (134) in a complementary manner with respect to the side of the locking pin receptacle (134) facing the locking bolt (132). Retaining arm (100) according to one of claims 2 until 4 , characterized in that the locking pin (132) is formed concavely on its side facing the locking pin receptacle (134), and in that the side of the locking pin receptacle (134) facing the locking bolt (132) is formed convex. Retaining arm (100) according to one of claims 2 until 5 , characterized in that the surface of the locking bolt (132) facing the locking bolt receptacle (134) and/or the surface of the locking bolt receptacle (134) facing the locking bolt (132) is formed with teeth (136). Retaining arm (100) according to one of claims 2 until 4 , characterized in that the locking pin (132) tapers conically or wedge-shaped at least in sections along its longitudinal axis, and that the locking pin receptacle (134) is set up to receive the locking pin (132) tapering conically or wedge-shaped. Retaining arm (100) according to one of claims 2 until 7 , characterized in that the locking bolt receptacle (134) is assigned at least one latching recess (172), into which a locking member can be engaged in the event of a traction mechanism tear, which is located between a wall (140) of the locking bolt receptacle (134) facing the locking bolt (132) and a the surface (142) of the locking bolt (132) facing the locking bolt receptacle (134). Holding arm (100) according to claim 8 , characterized in that the wall (140) of Locking bolt (132) is provided with a locking member receptacle (170) which has a wall which runs inclined with respect to the longitudinal axis of the bolt for guiding the locking member. Holding arm (100) according to claim 8 or 9 , characterized in that the locking member is formed from a material that is harder than the material of the locking pin (132) and / or harder than the material of the locking pin receptacle (134). Retaining arm (100) according to one of Claims 7 until 10 , characterized in that the locking pin (132) is formed with a recess (144) extending in its longitudinal axis, which is formed, in the event of a traction mechanism tear, the axis (118) of the blocked joint (108, 110, 114, 116) between to position oneself. Retaining arm (100) according to one of Claims 7 until 10 , characterized in that the locking bolt (132) is formed with two opposing contact surfaces (146) which are inclined with respect to its longitudinal axis, and in that the locking bolt receptacle (134) is set up so that the contact surfaces (146) of the locking bolt (132) in the case of the to clamp the traction mechanism crack between them. Holding arm (100) according to claim 12 , characterized in that at least one of the contact surfaces (146) is formed with a toothing (150). Method for fixing a holding arm (100) in position, in particular for fixing a holding arm in position according to one of Claims 1 until 13 , wherein the holding arm (100) has a proximal base part (102), a distal receiving part (104), a first arm extension (106) which is articulated at one end via a first joint (108) to the base part (102) and the other end is articulated to the receiving part (104) via a second joint (110), and has a second arm extension (112) which is articulated to the base part (102) at one end via a third joint (114) and the other end via a fourth joint (116) is articulated to the receiving part (104), a device (120) for compensating for the weight of a weight acting on the distal receiving part (104) being present, which comprises a spring (124) connected to a traction means (122), whereby if the traction mechanism (122) breaks, the potential energy stored in the spring (124) is at least partially released and transferred to a safety device (126), which then secures one of the joints (108, 110, 11 4, 116) stiffened. Securing device (126) for a holding arm (100) according to one of Claims 1 until 13 , with a connecting piece (130), with a locking pin (132) guided in the connecting piece (130), and with a locking pin receptacle (134).

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