The invention relates to an arm consisting of angu¬ larly displaceable linkages, such as a manipulator, having a fixed end carried by a support and a free end carrying a tool or workpiece, whereby each hinge is provided with controllable blocking means for the purpose of immobilising the linkages relative to each other.

The invention relates more particularly not to a driven arm, as is frequently the case with robots, but to an arm whereby the driving is effected by an external force, for example the manual force of the user. Known hereby is that the hinges between the linkages can be fixed in position or immobilised by blocking means, so that the free end of the arm stands still in a random position in the space as soon as the external force is removed and the hinges are blocked. Such an arm is used for holding an object in position for a long period, the supporting of loads and the like, tasks which for people would require much physical effort. Such an arm is for instance used in general surgery, for example for wound spreading. It is of importance hereby that the arm takes the most robust possible form in order to prevent, to the greatest possible extent, displacements caused by flexibility of the arm. A robust arm requires a comparatively heavy construction how¬ ever, which causes drawbacks with regard to the amount of force the user must exert at the free end of the arm in order to obtain a particular position. It is especially important in surgical applications that the user knows accurately which forces he is exerting on the tissue. The known arms of the type described in the preamble are not well suited to this purpose .

The invention has for its object to provide an arm obviating the above drawbacks , which arm is distinguished according to the invention in that in the case of one or more

pivot axes a member counterbalancing a turning moment is arranged to compensate the weight of the linkages freely mov¬ able relative to a hinge towards the free end.

Since the weight of the whole arm is entirely or almost entirely counterbalanced in all positions, the user can, by exerting a force on the head, know precisely what force he is exerting on the tool or workpiece clamped in the head, because the weight component of the arm itself is absent.

According to a further development of the invention the counterbalancing member consists of a housing connected firmly to the one linkage and having a chamber extending concentrically to the pivot axis and a reaction body accor- modated in the chamber and connected to the other linkage.

With such an embodiment the coun erbalancing mem- ber can be relatively small and arranged close to the pivot axis between the linkages.

In accordance with a first embodiment the reaction body can consist of a pivoting vane fitted in the chamber and connecting for sealing to the inner wall of the chamber. With such an embodiment a passive counterbalancing system is pos¬ sible by means of the resulting gas spring buffer as well as an active gas counterbalancing system. In the active embodiment one side of the chamber is in accordance with the invention connected to a pressure source, while the other side of the chamber communicates with the atmosphere.

According to yet another embodiment it is possible to execute the reaction member as a mechanical spring, for example a spiral spring.

The arm can in accordance with the invention be formed with blocking means which are formed by a bush-like balloon body connected to the one linkage and joinable to a pressure source, the cylindrical outer wall of which body ex¬ tends concentrically to the pivot axis and supports against a cylindrical inner wall concentric thereto of a hub-like body connected to the other linkage.

With such an embodiment of the blocking means rela¬ tively small hinge constructions are possible with a high

clamping moment , that is, a great frictional moment can be generated round the pivot axis.

Improvement of this moment can be brought about by arranging between the balloon and the hub strips to extend axially which are pressed by the balloon against the inner wall of the hub-like body.

Such a construction also lends itself to the immobi¬ lising of the head element of the arm in which the tool or workpiece can be accommodated. For this purpose according to the invention each strip is extended outside the hub-like body, which extended end portion is provided with a universal coupling of the head element. Owing to the universal coupling he head element is movable and turnable in all directions relative to the last linkage but one of the arm, which can ensure a great freedom of movement of the clamped tool or workpiece.

In preference the balloon body as ell as t e coun¬ terbalancing members at the hinges between the linkages are actuated pneumatically, whereby however two pneumatic supply systems according to the invention are used operating indepen- dently of each other. When the arm is moved through release of the one pneumatic system for the blocking members a free movement of the arm is obtained without the weight counter ^¬ balancing action being interrupted. The other pneumatic system is however suitable for accurate adaptation of the counter- balancing moment to a determined position of the arm as a consequence of the turning moment in the hinges being changed through displacement of the weight.

Above mentioned and other features will become apparent from the figure description hereinafter of two e - bodiments. In the drawing:

Fig. 1 shows a perspective view of a first embodi¬ ment of the arm, which is pneumatically actuated,

Fig. 2 shows on enlarged scale a perspective vie of a hinge between two linkages of the arm from fig. 1, where- by several parts are broken away,

Fig. 3 is a perspective top view on enlarged scale of the vertically positioned head element of the arm from fig. 1,

Fig. 4 and 5 show respectively the cross sections IV-IV and V-V from fig. 3,

Fig. 6 shows on enlarged scale a perspective view of a portion of the hinge between two linkages of a second embodiment ,

Fig. 7 is a side view of a third embodiment with parallel guiding.

The arm shown in fig. 1 consists of three linkages 1, 2 and 3 whereby it is assumed that linkage 1 is arranged for pivoting on a fixed support 4. The type of support is random and may have a flanged clamping base, suspension means for ceiling attachment or the like. The third linkage 3 has a free end protected by a rubber sleeve coupling 5 in which is coupled a head element 6 movable in all directions. Head element 6 serves to receive a tool or workpiece 7 of -random form.

In the embodiment shown the whole arm wit-h linkages can be turned on a vertical axis A-A (not further shown), while arranged between the linkages is a hinge with pivot axis B-B. Using such an arm the free end of linkage 3 can thus be placed at any random sρatia-1 coordinate, whereby the tool or workpiece 7 is still universally adjustable relative to this co¬ ordinate, this being further elucidated below.

There now follows a description of the hinge between the linkages embodied according to the invention, which is shown in detail in fig. 2. Although in fig. 2 the hinge between linkages 1 and 2 is shown, it will be apparent that such a construction can also be employed between the other linkages.

The hinge consists of a hollow spindle 11 connected rigidly to a side portion 10 of linkage 2. The hollow spindle 11 has on the right-hand side in fig. 2 a head 12 of square shape which fits into a correspondingly formed blind hole of a central body 13. This latter displays an end portion round the square blind hole to which is attached a bearing 14. Arranged adjoining the bearing is a part with screw thread 15 of greater diameter onto which can be screwed a sealing ring 16. Placed around the central body 13 is a balloon-shaped body 17, the

outer wall of which lies concentrically relative to spindle 11 and the free end edge of which lies clamped in position between the central body 13 and the ring 16, these and other matters such that an airtight connection is brought about. The other linkage 1 carries on its end a hub-like element 18 rigidly connected thereto which is formed on the inside with a cylindrical inner wall located concentrically to spindle 11. This is lined with friction material 19. Arranged between the friction material 19 and the balloon-shaped body 17 are a number of ^' strips 20 in segment form which are freely movable in a radial sense and which extend in axial direction parallel to spindle 11 and into the sealing ring 16. The hub-like body 18 is firmly attached to an end ring 21 supporting on bearing 14, which ring is bolted in position b means of bolts on a flange 22 of a housing 23 extending round spindle 11. This housing displays a chamber which has a segment-like form and extends concentrically relative to spindle 11. Firmly fixed to spindle 11 is a vane 24 which is provided along the periphery with a sealing strip 25 which makes a gas-tight connection to the inner wall of the segment-form chamber -23. The chamber is in addition provided with a flange 26 into which fits a gas- tight bearing 27 which supports on the spindle 11. Using such a construction the hub-like body 18 together with chamber 23 is therefore rotatable with linkage 1 about spindle 11, whereby on the other hand the spindle 11 with the vane 24 is rigidly con¬ nected on the central body 13 and the balloon-shaped body 17, this system moving with the linkage 2.

It is remarked that spindle 11 has a channel 28 which connects to a channel 28' in the central body which runs out into the outer wall of that body and communicates with the space bounded by the balloon-shaped body 17.

The chamber 23 further has a connecting stump 29 which can be attached to lines of a pneumatically or otherwise supplied system. The hinge thereby works as follows. If the channel

28 is not placed under pressure by a fluid, the balloon-shaped

body 17 will not be inflated and linkage 2 can turn freely- relative to linkage 1. As soon as a pressure is applied to the line 28 however, the balloon-shaped body 17 is brought under pressure, as a result of which the strips 20, which are freely movable in radial sense, are pressed against the friction material 19, which results in the effecting of a fixed connection between central body 13 and the hub-like body 18, which fixes the hinge and immobilises linkages 1 and 2 relative to each other. The space 30 on the upper side of vane 24 is brought under pressure via another pressure medium on channel 29, whereby a couple is generated as according to arrow V ι around spindle 11, which couple will tend to make the linkage 2 turn in the direction of arrow P ι . The pressure on the system is such that precisely the weight of linkage 2 and linkages con- necting thereto is counterbalanced. The other portion of cham¬ ber 23 communicates with the atmosphere via stump -31.

Should the arm however be turned such that linkage 1 moves through the vertical component, it will then be pos¬ sible to place the other portion of chamber 23 under pressure in order to be able to exert an opposing couple on the hinge and to thus counterbalance the weight then caused. The op¬ posite portion of the chamber on the other side of vane 24 is thereby placed in communication with the atmosphere.

Returning to fig. 1, the supply system is shown dia- grammatically therein. Via a control box 35, which is supplied by a pressure source (not shown), the lines 36 and 37 can be supplied parallel to each other with a pressure medium, for example air. The supply is kept separate by control box 35 such that, also when pressure from the pressure source falls away, the tension in lines 36, 37 is gradually eased to enable personnel to take action.

Supply line 36' can if required be arranged in order to obtain a dual control whereby control box 35 places either line 36 or line 36'in communication with the atmosphere. A description now follows of the coupling of the head element 6 on the final linkage 3, which element is rec ^¬ koned to be fixed to the central body 13 of a longitudinal

hinge on the free end portion of linkage 3. For the sake of clarity the same reference numerals are used for the same components of the longitudinal hinge. Also employed here is a balloon-shaped body 17 which extends concentrically of the pivot axis B-B. Ordered around the body are axially extending bodies in segment form, see also fig. 4, against the outer side of which lie strip-like elements 20. Arranged between the strip- like elements 20 and the hub-like body 18 is a friction material 19. In this embodiment of the longitudinal hinge the strip-like bodies 20 extend far outside the hub-like bod 18, hereby they protrude through sizeable openin s 41 in the upper and/or lower head flange 42 and can therefore undergo a free movement in axial as well as radial sense relative to the hub-like body 18.

Mounted on the lower end of each strip 20 is a universal coupling 43 which is connected to a fastening bolt 44 forming part of head element 6. Fitted in the embodiment shown are four elongate strips 20 which are each provided with a universal coupling 43 so that there are four ordered in a circular arrangement. Head element 6 and a sealing face 45 joined to the hub-like element 18 are coupled to each other by a fifth universal coupling 46. This permits a rotation of head element 3 relative to the final linkage 3 but no axial change. The head element 6 is built up of a number of parts attached to one another for accommodation of different func ^¬ tions thereof. The head element 6 may of course take another form.

The element is provided with a blind bore 50 into which the shank 75 of for instance the tool or workpiece 7 is inserted. Protruding into the bore of element 6 are noses 51, four of which are arranged in the embodiment shown. Arranged in the head above the noses is a groove-like recess 52 in which a locking member 53 is rotatable on a spindle 54. The latter can be rotated by means of a manually operated lever 55 coun¬ ter to the action of a drawback spring 56.

By inserting the shank 51, which is also provided with protruding noses 57, these noses 57 can be carried past the noses 51 and be rotated through 90 above the noses 51. By adjustment of lever 55 the locking member 53 can then be carried into the space between noses 57, see fig. 5, whereby the tool or workpiece is non-rotatably locked in the blind bore of head element 6.

Release of the tool or workpiece is carried out in reverse sequence and it will be understood that with the em- bodiment shown differently formed tools or workpieces can be arranged in easy manner in the head element 6.

The head element 6 further displays a portion pro¬ vided with a release channel 60 that is furnished with a release valve 61 actuated by a push button 62. Channel 60 connects onto the supply line 37 for inflation of the balloon-shaped bodies 17 in the hinges.

The channel 60 is formed in the head with a branch line 63 which leads to a release valve with smaller passage opening 64 located on the other side, which is actuated by a push rod 65 that forms part of a lever 66 turnable relative to head 6.

The purpose of the push button 62 and lever 66 is in one respect the rapid release of the pressure in the line 37, which results in the hinges suddenly becoming pressureless and the arm becoming freely movable because it is channel 37 which serves to supply the balloon-shaped "bodies 17 in the hinges .

In the case of accurate displacement whereby the pressure only need be released partially, the lever 66 is operated such that only a small quantity of air can escape via branch channel 63 and release valve 64, as a result of which turning movement under friction of the different linkages relative to one another is possible.

It will be apparent that with the shown hinge con- struction of the head element 6 a particularly robust but com¬ paratively small construction is obtained, whereby by placing the system 37 under pressure the gripped tool or workpiece is

held motionless in the space in the finally set position without displacement resulting from flexibility in the arm.

Fig. 6 shows in detail a second possible embodiment of the weight counterbalancing member. Arranged around spindle 70 is a chamber 71 connected concentrically to the one linkage 1'. The spindle 70 is rigidly connected to the second linkage 2'. Fitted between spindle 70 and the inner wall of chamber 71 is a counterbalancing member in the form of a spiral spring 72. Depending on the weight to be counterbalanced the length of the spiral spring and the spring constant can be of a mag¬ nitude such that as a result of displacement of the arm the counterbalancing moment round the spindle 70 hardl varies from the turning moment round spindle 70 as a consequence of the shifting weight of the linkages. Fig. 7 shows a third embodiment wherein each linkage is built up of two parallel or virtually parallel rods 80, 81 which are each mounted for pivoting relative to a hinge sup¬ port 82. The support 82 can be mounted for swinging about a vertical shaft 85 relative to a work table 86. The head ele- lent 61 is assumed to be of a like construction to that shown in fig. 3, whereby the part 18 thereof functions as hinge support for the rods 80' and 81'. In accordance with a feature the one rod 80, 81' of a linkage is provided at a pivot axis thereof with the counterbalancing member with vane 24 as shown in fig. 2, and the other rod 81, 81' with a blocking member as shown on the right in fig. 2 and provided for instance with a rubber sleeve coupling 17. The operation of blocking and coun¬ terbalancing members, and therefore of the manipulator arm, is the same as that of the arm described as according to fig. 1, with the proviso that the support 18 of the head element will retain the same spatial position during displacement.

The invention is not limited to the above described embodiments .

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