Three-dimensionally adjustable arm

Abstract

A three-dimensionally adjustable segmented arm 10, especially a robot arm, which has a centreline 11, comprises a succession of interconnected and relatively rotatable segments I to VI positionable in

Description

The present invention relates to a three-dimensionally adjustable arm, especially a robot arm, but more generally an arm serving as a support, carrier, holder or any other purpose where versatile adjustability relative to, for example, a mounting or other reference point may be desired. A challenge faced when designing robot arms is that of devising means by which the arm can operate in the entirety, or close to the entirety, of the space within the compass of the arm as defined by its reach. The exploitable space is typically referred to as the workspace of the arm. The problem is not limited to robotics. The joints of living creatures have a residing shortcoming in that they circumscribe the exploitable workspace, as demonstrated by the deficiency of the human arm when reaching behind the neck or when attempting to attain the zone between the shoulder blades. In analogous fashion, robot arms encounter zones that they cannot enter. The issue arises when joints align in a way that prevents smooth, continuous motion. Joint-seizure can be severe enough to exclude continued movement along a desired trajectory, rendering a task unachievable. Further challenges are encountered in the design of robot arms, notably when the purpose is to maximise the ability of an arm to perform useful work under the influence of gravity while not sacrificing reach and direction-change versatility. The obligatory compromise is between the ability of the arm to overcome its own weight in order to lift an object or to apply mechanical force, and the length extension of the arm and ability to change direction at intervals along its length in order to reach desired locations and to move around objects. The two requirements are mutually constraining. Large actuators capable of generating large forces necessarily incur a greater mass penalty than do smaller actuators. A plurality of joints, preferably a minimum of six to impart to the arm a good capability of movement in the x, y and z axes and to rotate around these same axes, is a prerequisite for achieving the versatility required to perform many tasks. This requirement, however, multiplies the number of actuators and necessarily incurs a greater mass penalty than does a lesser number and, in so doing, impacts negatively on the force-application capability of the robot arm. In the format of joints generally selected for so-called vertical axis serial arms as used widely in industrial automation, this arrangement, when associated with the geometry of their joints, has a number of shortcomings. While the design of the means of actuation of the arm plays an important role, notably the relationship between the available torque and power of the actuator and its mass, the joint design plays a decisive role in determining the relationship between mass, the reach of the arm, its direction-change capability and the available applicable force at full reach. The interdependency of these characteristics is evident when considering industrial automation robot arms comprising six joints, three of which are oriented along the same axis. Examples of these include the robot arm 'ABB IRB 1200' of ABB Ltd of Vasteras, Sweden I Zurich, Switzerland, and the robot arm 'UR16e' of Universal Robots USA, Inc., of Novi, Michigan, United States. This arrangement of joints associates three actuators with direction change in a single axis. In an industrial automation context, direction change in a single axis along much of the length of the robot is generally considered appropriate and adequate for the tasks the arm is required to perform, as the workspace can be arranged to suit the reach and direction-change capabilities of the arm and there are typically few or no obstacles to avoid. A further example of a multi-joint robot arm of such a kind is disclosed in the specification of US Patent Application US 2011 / 0757786 A1, in which the arm is composed of segments, some of which have inclined terminating faces. These faces co-operate with faces of adjacent segments, in particular faces that lie in planes perpendicular to the segment axis. There are, however, many instances in which the ability of the robot arm to reach around obstacles and to perform tasks while avoiding parts of the workspace and, in so doing, not sacrificing force-application ability, would be desirable. These requirements are not met by the technologies currently available. Applications for an arm of this type are to be found in nuclear decommissioning, maintenance and repair in industrial and space contexts, warehousing and logistics, waste sorting and recycling, the fields of defence, security and first responder and in a range of manufacturing applications. In all these instances, the operational environment may be crowded with objects or may be difficult to access or both, calling on a need for the arm to be able to reach around and avoid obstacles and be capable of following indirect paths to a target position. In many instances it may not be possible to optimally place the base or origin of the arm in relation to the workspace and once again the arm must be able to reach around and avoid obstacles and be able to operate in the entirety, or close to the entirety, of the workspace in order to be useful and commercially viable. A further challenge arises when the task requirements change unpredictably, requiring adaptation by the robot arm and specifically calling on its directionchange ability. In a typical bomb-disposal scenario an initial appraisal of a task frequently obliges a bomb-disposal expert to revise a plan-of-action and set about disabling an explosive device by means not envisaged at the outset. The reach of the robot arm and its ability to avoid objects become critical factors in this instance as they enable the robot arm to adapt to a new set of requirements. The ability to operate in the entirety, or close to the entirety, of the workspace can be a decisive factor when undertaking tasks such as the 3D printing of structures, paint spraying, abrasive jet cleaning, delaminating and the like. To perform these tasks with precision and cost-effectively it is critical for the robot to be able to move freely throughout the workspace and to deploy an appropriate tool head without the need to avoid certain zones. A robot arm with these capabilities removes the need to arrange or re-arrange the workspace, or to adjust the positioning of the arm within it, in order to compensate for the deficiencies of the arm. Software work-arounds are common practice when using serial vertical axis arms and typically much effort is devoted to avoiding the parts of the workspace where the robot cannot operate. Arms designed to perform direction-change at many intervals along their length include the robot arm 'snake arm [Registered Trade Mark] 101' of Oliver Crispin Robotics Ltd of Filton, Bristol, United Kingdom and the 'elephant trunk' robotic manipulator of Clemson University, Clemson, South Carolina 29634, United States. Conceptually, these arms take inspiration from snakes, emulating their sinuous shape-changing capability. The Oliver Crispin Robotics arm has a functional advantage over industrial automation arms in that its generally smooth and uninterrupted external geometries lend it to use in confined spaces where it is unlikely to snag on features in the environment. The Clemson University arm, suitably sheathed, is also suited to operation in confined spaces and by virtue of tapering along its length is less likely to snag and become immobilised than an arm having the same cross-section along its length. Arms of this kind may lack robustness, however, and this may limit their usefulness. In the case of the Oliver Crispin Robotics arm, reliance is made on the deformation of an external casing which of necessity must be manufactured from a pliable material which, with repeated deformation, might fail mechanically. In the case of the Clemson University arm, reliance is placed on extension and compression of a large number of springs which, with extended use, may be susceptible to mechanical failure. The method for creating direction change for both these types of robot arms relies on complex and inherently fragile actuation mechanisms with the function of varying the tension of a large number of cables. These cables act upon transversal flanges which are mounted at frequent intervals along the arm length and which, in movement, deform the outer casing of the arm and thereby generate direction change. Mechanisms of this type, being reliant on extended cables and flanges that are necessarily lightweight in order to minimise the mass penalty of the arm, are inherently limited in terms of the forces they can exert, and as a consequence the force-application and lifting capability of the arm may be diminished. This factor in turn compromises practicality and usefulness. A further issue arises in relation to the system required to extend and retract a large number of cables, as this tends to be bulky and cumbersome, and in some cases as many as fifty electromagnetic motors may be employed. Bulky systems like this are unsuitable for many applications where space is a constraint. Reliance on the deformability of the external casing and the necessarily small range of movement obtainable at any one flange has a further disadvantage, as robot arms of this type are inherently limited in terms of the range of direction change achievable at any given position along their length. They are, as a consequence, unable to perform abrupt turns, for example achieving an internal angle at a given position along their length or over a relatively short portion of their length, a requirement which arises when the robot arm is used to access more confined and difficult-to-reach spaces. It is therefore the principal object of the invention to provide a three-dimensionally adjustable arm, for example a robot arm or a support or carrier arm, with enhanced scope for three-dimensional adjustment or reconfiguration by comparison with prior art designs. Other objects and advantages of the invention will be apparent from the following description. According to the present invention there is provided a three-dimensionally adjustable segmented arm having a centreline and comprising a succession of interconnected and relatively rotatable segments positionable in selectable rotational settings relative to one another, and fixing means for fixing the segments in selected rotational settings, wherein the segments of at least one pair of two adjacent segments in the succession are rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment and wherein the planes of those two segments extend obliquely at the same angle to the respective parts of the centreline present in the two segments, the angle being selected so that those two segments are rotatable relative to one another between a setting in which the parts of the centreline therein are aligned with one another and a setting in which the parts of the centreline therein include an acute angle. An arm embodying the invention can be used as, for example, a robot arm, thus an arm fixed or located at one end and provided at the other end with a tool, instrument or other useful device or more usually just with means for attaching such a tool, instrument or other device. The formation of the arm from a succession of segments of which those forming at least one pair of adjacent segments are rotatable relative to one another - but preferably the adjacent segments of each of a plurality of pairs - about the stated axes enables the relatively rotatable segments of the or each pair to be displaced between an end setting in which the parts of the centreline present in the segments concerned are aligned with one another and an end setting in which those parts include an acute angle, i.e. any angle of less than 90 degrees, thus settings in which the section of the arm composed of two relatively rotatable segments is straight and a setting in which it is angularly bent back on itself to a greater or lesser extent depending on the selected angle of obliquity of the associated terminating planes. It will be understood that in the case of a succession of segments, consecutive pairs of segments may share segments: thus, for example, in a succession of three segments designated one, two and three a first pair can be represented by segments one and two, which are rotatable relative to one another, and the next pair represented by segments two and three, which are also rotatable relative to one another. Two couplings of the segments or joints of the segmented arm are then present in that succession of three segments. If all segments of the arm are paired in this way, thus each segment of the arm is rotatable relative to the or each adjacent or neighbouring segment, a particularly high level of capability of reconfiguration of the arm in three dimensions is achievable. The arm is then capable of multi-dimensional contortion to allow maximum exploitation of a three-dimensional workspace, especially to follow indirect paths to avoid obstacles or more generally to avoid and circumnavigate particular parts of the workspace. For preference the angle which each of the obliquely extending terminating planes of the at least two segments includes with the part of the centreline present in the respective segment lies in a range of less than 45 degrees and more than substantially 22 degrees. An angle at one extreme of this range, i.e. that of less than 45 degrees, for example 44.5 degrees, provides only a minimum amount of bending back of the two segments on themselves and at the other extreme of the range, i.e. that of more than substantially 22 degrees, for example 22.5 degrees, provides a maximum desirable amount of bending back of those segments. Although an included angle of less than 22 degrees is possible, in terms of practicality such an extent of bending of adjacent segments back on themselves is usually not needed and may complicate arm construction and mobility, particularly if it results in segments of the arm at a distance from another being able to be brought too readily into undesired conflict under contortion of the arm. In one preferred embodiment the segments of the succession comprise a plurality of pairs of two adjacent segments rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment, wherein the angles at which the terminating planes of the segments extend obliquely to the respective parts of the centreline present in those segments are substantially identical for all the segments of that plurality. This embodiment represents a simplified arm construction with advantages of economy resulting from the possibility of use of identical segments. In effect, the segments of each pair present in the arm are rotatable relative to another through the same range of settings, that is to say a setting in which the arm will be entirely straight and a setting in which, at each junction of two adjacent segments, the arm is capable of being maximally bent to the same angle. In another preferred embodiment offering tailored variability in arm adjustment or reconfiguration capability, at the expense of more complicated arm construction, the segments of the succession comprise a plurality of pairs of two adjacent segments rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment, wherein the angles at which the terminating planes of the segments extend obliquely to the respective parts of the centreline present in those segments are different for at least some of the segments of that plurality. In this case the range of settings between which the adjacent segments of individual pairs are adjustable can differ at selectable points in the arm. For example, in end regions of the arm there may be no advantage or it may be inappropriate for the arm to be able to be bent back on itself. Accordingly, the segments of a pair at the end of an arm may be relatively rotatable about axes perpendicular to terminating planes having such an angle to the parts of the centreline in those segments that the segments are adjustable between a setting in which those centreline parts are in alignment and a setting in which the centreline parts include an angle greater than 90 degrees, thus an obtuse angle. Depending on the functional requirements of a particular arm the pairs of adjacent segments in the succession can be constructed, in particular by selection of the obliquities of their terminating planes and hence of their axes of relative rotation, to be capable of different maximum bending angles of the arm at different junctions of the segments along the arm. The adjustability of the arm may be enhanced if at least one of the segments of the arm comprises two sections rotatable relative to one another about an axis coincident with the part of the centreline in that segment. In that case, relative rotation of the two sections allows the two lengths of the arm either side of those sections to be turned relative to one another so as to bring a particular point of the arm, such as at a free end thereof, into a specific defined position in space without the necessity of relative rotation of the adjacent segments of one or several pairs to achieve this. This provides an additional adjustment capability of the arm, which is particularly helpful for precise positioning of the arm in use. In yet another preferred embodiment at least one of the segments in the succession is rotatable about a first axis perpendicular to a first terminating plane thereof relative to a first adjacent one of the segments in the succession and about a second axis perpendicular to a second terminating plane thereof relative to a second adjacent one of the segments in the succession, wherein the first and second axes are angularly offset relative to one another about the part of the centreline present in the at least one of the segments. An individual segment can therefore be configured so that it is rotatable relative to two adjacent segments - thus a segment on either side - about axes which lie not in the same radial plane of the part of the centreline in that individual segment, but in different radial planes. The two terminating planes of that individual segment will thus be turned relative to one another about the centreline, more particularly the part of the centreline in the segment. This feature allows tailoring of the arm to a desired capability of reconfiguration, for example if the intended place of use or installation of the arm imposes a requirement for bendability of the arm in a particular direction at a particular point in its length or if simply a wider or different range of variability of the arm adjustment is desired in general use. In order to promote compactness of the arm particularly in an adjusted state with multiple bends, each terminating plane includes an acute angle and an obtuse angle with, respectively, two opposite sides of the part of the centreline present in the respective segment and defines a terminating face of that segment, the face and therewith the segment being truncated at the side of the centreline part with the obtuse angle. This feature effectively shortens the segment and, especially, removes a portion of the segment which would otherwise form a pointed projection when that segment and the adjacent segment are relatively rotated into the end setting in which the respective parts of the arm centreline include the acute angle and indeed also intermediate settings around that end setting. Truncation of the segment in the manner described thus removes a potential snagging projection when the segment and an adjacent segment are not in alignment. In further preferred embodiment at least two of the segments are of respectively different dimensions in the direction of the parts of the centreline therein. Thus, the segments can be of differing lengths in the length direction of the arm according to requirements. If, for example, a capability of bending the arm does not arise until a distance from a mounting or support end of the arm the segment at that end can be suitably longer. This may reduce the constructional cost of the arm. Equally, if so desired the dimension of the arm transversely to the centreline can reduce over the length of the arms between mutually opposite ends thereof. This feature can be utilised to achieve less weight towards a free end of the arm so as to reduce gravitational loading of the arm, particularly since the arm will generally have cantilever mounting or support, or in a converse sense to provide increased strength and stability at or towards a mounting or support end of the arm. The segments can be of a desired suitable shape, but expediently each of the segments has a substantially cylindrical circumferential surface between its oblique terminating planes. This may in a given case allow simplified manufacture from lengths of a cylindrical rod or tube, but more particularly provides a circumferential form compatible with the rotation of the segments about axes. In one preferred embodiment the fixing means is arranged to fix the segments in selectable rotational settings by a mechanically positive couple, which ensures that the segments are firmly locked together to maintain every selected configuration of the arm. Such a couple can be provided by, for example, a sliding detent system, which may be arranged to permit relative rotation in increments, with periodic locking, such as by a spring-loaded ball selectively engageable in the recesses of a series of recesses. However, other forms of a sliding detent system are conceivable, as are other ways of realising a mechanically positive couple. In another preferred embodiment the fixing means can be arranged to fix the segments in selectable rotational settings by a friction couple, for example by way of friction surfaces resiliently biased into contact. This may allow continuous relative rotation, i.e. otherwise than in incremental steps, of relatively rotatable adjacent segments in cases where, for example, the junctions of the segments of the arm are not unduly loaded by gravitational force liable to overcome a friction couple. The segments of the arm can, in the simplest case, be relatively rotated manually. This may be appropriate particularly in the case of design of the arm for use simply as a support or carrier of a device needing to be positioned in a range of different elevations, rotational orientations andlor angles. In the case of, especially, a robot arm designed to be controlled remotely or to be adjusted in a preprogrammed manner it is advantageous if the arm comprises drive means accommodated in the segments and operable to selectably rotate each two adjacent segments in the succession relative to one another. Such drive can comprise, for example, actuators individually associated with the junctions of the segments. A combination of actuation by drive means and manual actuation is also possible, either for different segment junctions or the same segment junctions. If drive means are present, the fixing means can, if desired, then be provided by the drive means in non-operating state, for example a motor or other form of actuator which is immobile and locked in the absence of operating energy. Alternatively or additionally, the fixing means may comprise an arresting brake co-operable with the drive means. In a preferred realisation of the arm it is provided at one of two mutually opposite the ends thereof with mounting means for mounting on a support. The mounting means be of any desired and suitable kind, for example a weighted base or a base securable to the support. Moreover, the arm may be provided at the other one of the two ends with attaching means for attaching an implement, tool or other useful or utility article, for example, in the case of a robot arm a manipulator or pick-up, and in the case of a support or carrier arm a mount for an instrument, image recording, sound recording or lighting equipment or other device for performing a task. The range of use of the arm is extensive and not limited to the few given examples. Preferred embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic elevation of a first three-dimensionally adjustable segmented arm embodying the invention; Fig. 2 is a simplified schematic elevation similar to Fig. 1, but to a smaller scale, of a second three-dimensionally adjustable segmented arm embodying the invention, showing differently angled terminating planes of segments of the arm; Fig. 3 is a simplified schematic elevation similar to Fig. 1, but to a smaller scale, of a third three-dimensionally adjustable segmented arm embodying the invention, showing different rotational angle relationships of segments of the arm; Fig. 4 is a simplified schematic elevation similar to Fig. 1, but to a smaller scale, of a fourth three-dimensionally adjustable segmented arm embodying the invention, showing different lengths of segments of the arm; Fig. 5 is a simplified schematic elevation similar to Fig. 1, but to a smaller scale, of a fifth three-dimensionally adjustable segmented arm embodying the invention, showing different diameters of segments of the arm; Fig. 6 is a schematic perspective view of a sixth three-dimensionally adjustable segmented arm embodying the invention, showing an exemplifying configuration achievable by adjustment of the arm; Fig. 7 is a view of the arm of Fig. 6 in a different exemplifying configuration; and Fig. 8 is a view of the arm of Fig. 6 in yet another exemplifying configuration. Referring now to the drawings there is shown in Fig. 1 a schematic elevation of a first three-dimensionally adjustable segmented arm 10, particularly an arm intended as a robot arm, in a basic form. The arm 10 has a centreline 11 which is rectilinear in the illustrated arm configuration, but which is resolved into relatively angled parts in the case of bent and / or contorted configurations which the arm is capable of assuming as described further below. The arm 10 is principally composed of a plurality of relatively rotatable segments, which are designated I, II, III, IV, V and VI in Fig. 1. The number of segments is selectable in accordance with, inter alia, the intended use of the arm. Fig. 1 shows six segments, which provides an arm of useful length and versatile adjustability without unduly multiplying the total number of auxiliary components normally associated with the segments. However, a greater or lesser number of segments is equally possible. The segments I to VI each have a cylindrical outer circumferential surface and are typically hollow or otherwise formed with through passages to allow hydraulic, pneumatic, micro-fluidic and / or electrical feed lines and / or tubes to run through the arm between its ends for the purpose of supply or transmission of operating media, control media, control signals and / or data,. The segments can be produced by machining from alloy, additive layer manufacture from plastics or metallic material, casting or any other suitable method. Each of the segments I to VI has at least one terminating plane 12 extending obliquely at an angle to the centreline 10; two terminating planes 12 are present in the case of each of the segments II to V. The segments adjoin one another at those planes, which thus represent junctions of the segments. The segments are connected together by suitable connecting means (not shown) at the junctions to form an assembly, i.e. the segmented arm 10, but are capable of rotation relative to one another. In particular, the segments of each adjacent pair of segments, namely the pairs l / ll, ll / lll, Ili / IV, IV / V and V / VI, are rotatable relative to one another about a shared axis 13 extending perpendicularly to the oblique terminating planes 12 present at the junction of those segments. Each of those planes includes a selected acute angle, designated 14 in Fig. 1, with the part of the centreline 11 present in the respective segment, that angle being the same for the two planes. In the case of the simplified arm of Fig. 1 the selected angle is common to all of the segments I to VI. If the basic dimensions of the segments II to V are also the same, namely length and diameter, the segments II to V can be identical, which may simplify production and reduce cost. A feature of the embodiment of Fig. 1 and of all other embodiments is that the angle 14 is selected to allow each two adjacent segments to be rotatable relative to one another between an end setting in which the parts of the centreline 11 in those segments are aligned with one another, in which case the portion of the arm 10 containing those segments is straight as shown in Fig. 1, and a setting in which those parts of the centreline include an acute angle, thus an angle of less than 90 degrees, in which case the portion of the arm containing those segments is bent back on itself to a greater or less extent. Between the end settings, the two adjacent segments will, under relative rotation, produce a bend in the arm of a variable - and selectable - angle lying below 180 degrees and above the stated acute angle, thus an angle varying in a range composed of both obtuse and acute angles. The angle 14, namely the angle each terminating plane 12 includes with the relevant part of the centreline 11, is preferably selected to lie in the range of less than 45 degrees and more than 22 degrees, for example 44.5 degrees and 22.5 degrees. The smaller the included angle 14, the greater the slope of the plane 12 and the greater the extent of return bending of the arm 10 able to be achieved at that plane. Angles smaller than 22.5 degrees are entirely possible, but the sharper bends that result may be accompanied by penalties of complication in, for example, connection of the relevant segments and potential collision, under segment relative rotation, of segments producing such bends As can be seen in Fig. 1, each of the terminating planes 12 includes an acute angle, i.e. the angle 14, and an obtuse angle (not designated) with, respectively, two opposite sides of the part of the centreline present in the respective one of the segments and defines a terminating face of that segment (also not designated, since it is coincident with the plane). That face and hence the respective segment are truncated at the side of the centreline part with the obtuse angle, in particular by a truncating surface 15. The truncating surface 15 eliminates a length portion of the segment which would otherwise form a pointed projection potentially capable of snagging an object or structure in an area or workspace where the arm 10 may be located in use. The arm 10 is fitted, in this embodiment, at one of its two opposite ends with a base 16 for supporting the arm on a support, which may be, for example, horizontal or vertical. The base, which can be designed to be securable to the support by suitable securing means, is coupled to the arm, in particular the adjacent end segment VI, by a motorised joint providing rotation of the segments as a whole about the part of the centreline 11 in the segment VI. At the other one of its ends the arm has a mount 17 for a tool, such as a manipulator, pick-up, grippers, sensor or any other utility device. Similarly to the base 16, the mount 17 is coupled to the arm, in particular the adjacent end segment I, by a motorised joint providing rotation of the mount relative to the segment I about the part of the centreline 11 in the segment I. The base 16 and mount 17 enable the arm to perform a work operation in a workspace. Relative rotation of two adjacent ones of the segments can be provided by a suitable actuator, motor or other drive associated with those segments, the drives of whatever form being operable, for example, hydraulically, pneumatically, electrically or electromagnetically. Fixing of those segments against relative rotation when they are located in a desired relative rotational setting can be provided by a suitable fixing device or even by the actuator, motor or other drive itself when in a non-operating state. A drive and a fixing device are symbolically indicated by dashed lines 18 at the junction of the segments III and IV and constitute a motorised joint. Such a joint - thus drive and fixing device - is provided at each of the segment junctions. Suitable forms and concepts of drives and fixing devices for segmented robotic arms are known in the art. As evident from the foregoing description, under relative rotation of adjacent segments forming a pair, thus l / H, ll / lll, II l / l V, IV / V or V / VI, a bend can be produced in the arm 10 at the location of the adjacent terminating planes 12 or junction of those segments. A bend can be produced as desired at each such junction, whereby adjacent segments can extend in diverse directions within a spatial range of 360 degrees. The arm 10 is accordingly adjustable to create a particularly wide range of configurations, as exemplified further below in connection with discussion of Figs. 6 to 8, thereby allowing the arm to make optimal use of the workspace in which it is located. These configurations include contortions of the arm 10 in which two adjacent segments may extend with components in the same direction, thus producing in the arm a bend in which the arm extends, so to say, to an extent back on itself. With advantage, each or at least some of the segments may be equipped with a sensor to detect a load resulting from relative rotation of two adjacent segments or a load applied by a tool or other device mounted on the mount 17. A further adjustment capability of the arm 10 may be achieved if one of more of the segments consists of two sections rotatable relative to one another about the part of the centreline 11 present in the segment. This is exemplified in Fig. 1 by construction of the segment II from two sections HA and I IB, which meet at a plane 19 perpendicular to the respective part of the centreline. Dedicated drive means (not shown) can be provided for rotating the two segment sections HA and HB relative one another as well as fixing means (also not shown) for locking the two sections in a set relative rotational angle within a 360 degree range. Division into two such segments can be provided for any one or any number of the segments I to VI. This additional adjustment capability is of particular assistance for precision location in azimuth of a tool carried by the mount 17. As already mentioned, Fig. 1 shows a basic arm 10 with constant relationships of the adjacent segments and constant segment dimensions. Figs. 2 to 5 show, in highly schematic and simplified diagrams, variations of segment relationships and dimensions within an arm. These illustrated variations are merely examples to demonstrate concepts rather than specific arm constructions. The concepts can be realised in various ways or combined with one another to construct arms with individual adjustment capabilities, thus reconfigurability, tailored to specific tasks. Fig. 2 illustrates, in simplified and diagrammatic form, a variant of the segmented arm 10, in particular a segmented arm 20 which has a centreline 21 and in which segment terminating planes 22 corresponding in purpose with the planes 14 of Fig. 1 each include with the centreline an angle which - in departure from the corresponding angle 14 of Fig. 1 - differs along the length of the arm. As a consequence, the axes, which are designated 23, of relative rotation of the segments of the arm 20 are variably oriented so that the relative rotation produces different degrees of return bending of the arm in the related end settings of adjacent segments. In an example, the included angles with smaller values may be situated closer to the lower (base) end of the arm and those with greater values closer to the upper (mount) end of the arm, but the disposition of the different included angles and hence different obliquities of the terminating planes 22 and angles of the axes 23 can be freely selected in accordance with, especially, the intended task of the arm, the workspace in which it is to be situated and presence of obstacles in or intrusions into the workspace. Fig. 2 shows merely an arbitrary disposition of the differently angled axes 23 for the purpose of illustration of this feature. Fig. 3 illustrates, again in simplified, diagrammatic form, a further variant of the segmented arm 10, in particular a segmented arm 30 which has a centreline 31 and in which segment terminating planes 32 corresponding in purpose with the planes 14 of Fig. 1 include planes offset about the centreline 31 relative to the remaining planes. In particular, as shown in Fig. 3, in which the segments of the arm 30 are for convenience marked I to VI in correspondence with Fig. 1, the terminating planes 32 at the junctions of adjacent segments making up the segment pairs l / ll, lll / IV, IV / V and V / VI have the same angular disposition about the centreline 31, but the planes at the junction of the segments of the pair Il / llI are offset about the centreline in relation to the other planes. The offset in this example is 90 degrees, but could be any desired angle. Thus, the segment II is rotatable relative to the adjacent segment I about a first axis perpendicular to the planes 32 at the junction of segments I and II and rotatable relative to the other adjacent segment III about a second axis perpendicular to the planes 32 at the junction of segments II and III, the two axes being angularly offset relative to one another about the centreline 31. A truncation surface 33 corresponding with one of the surfaces 15 in Fig. 1 is marked on the segment II of Fig. 3. Fig. 3 shows merely an arbitrary location of the angularly offset planes / axes, namely at the junction of the segments II and III. This feature can be provided at any one of the junctions of adjacent segments and at more than one of the junctions. Fig. 4 illustrates, once more in a simplified and diagrammatic form, a further variant of the segmented arm 10, in particular a segmented arm 40 which has a centreline 41 and in which the constituent segments - again designated I to VI - have in part different dimensions in the direction of the centreline or length of the arm. By way of arbitrary example, the segments II and III are of approximately the same length as one another, but shorter than the segments IV and V, which also have approximately the same length as one another. If so desired, the segments can all be different from one another in length, but it is preferable in terms of manufacturing cost if some segments are of the same length and can thus be identical. The disposition of different segment lengths along the arm 40 can also be selected as desired, but a reduction in segment length at a distance from the lower or base end of the arm may usefully reduce segment weight in the region of the arm furthest from its support. Analogously to the arm variant of Fig. 4, Fig. 5 diagrammatically 4 illustrates yet another variant of the segmented arm 10, in this case a segmented arm 50 which has a centreline 51 and in which its segments - once more designated I to VI - have in part different diameters or widths transversely to the centreline. In this instance the reducing segment diameter advantageously reduces segment weight in the region of the arm furthest from its support so as to reduce loading of segment drives (not shown) incorporated in the arm. As in the case of the variant of Fig. 4, the reduction in segment diameter preferably takes place in stages. By way of arbitrary example, the segments I, II and III are of the same diameter as one another, but narrower than the segments IV, V and VI, which also have the same diameter as one another. Again, if so desired the segments can all be different from one another in diameter, but it is beneficial to manufacture if some segments are of the same diameter and can thus be identical or, at least, employ identical drives. The disposition of different segment diameters along the arm 50 can also be selected as desired, but the object of minimising load is served by reduction in diameter and hence weight in a region distant from the lower or base end of the arm. Contribution to reduction in weight in this region can be the use of smaller size drives permitted by the smaller diameter segments. It is emphasised that although the arms 10 to 50 of Figs. 1 to 5 have been presented as individual embodiments this is merely to facilitate description and illustration of the respective characterising features. In practice, some or all of those features may be present singly or multiply in an individual segmented arm, thus an arm with different angles of terminating planes (axes of segment relative rotation) and / or planes / axes angularly offset relative to one another about the arm centreline and / or different segment lengths and / or different segment diameters / widths. The capability of the arm 10 or any of the arms 20 to 50 to adopt different configurations under relative rotation of the segments of one or more adjacent segments in the arm will be apparent from the foregoing description of preferred embodiments and the associated Figs. 1 to 5. Examples of attainable configurations are shown in Figs. 6 to 8, which show a further embodiment of the segmented arm, in this case an arm 60 composed of five segments XI, XII, XII, XIV and XV (marked only in Fig. 6) with features derived from not only from the arm of Fig. 1, but also from the arms of Figs. 3, 4 and 5. These features include, in the case of the segment XII, oblique terminating planes angularly offset relative to one another about the part of the centreline (not shown) of the arm in that segment, thus the feature described with reference to Fig. 3, and segments of different length and diameter as described with reference to Figs. 4 and 5. It will be self-evident that the depicted configurations assumed by the bent arm are merely an arbitrary selection from a countless number of possible configurations. By virtue of the adjustability of the arm and the variability in the basic arm construction available from selection of, for example, different arm lengths, number of segments, angles of segment terminating planes (axes of segment relative rotation) and other parameters, a robot arm can be realised which may be able to fully exploit the entire volume of any three-dimensional workspace in which the arm is to operate. If the arm is to serve merely as a support or carrier of an item of equipment, for example a 3D scanner, the adjustability of the arm may allow the equipment to be moved into and positioned in almost any desired location and orientation.

Claims

1. A three-dimensionally adjustable segmented armhaving a centreline and comprisinga succession of interconnected and relatively rotatable segments positionable in selectable rotational settings relative to one anotherand fixing means for fixing the segments in selected rotational settings,wherein the segments of at least one pair of two adjacent segments in the succession are rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment,and wherein the planes of those two segments extend obliquely at the same angle to the respective parts of the centreline present in the two segments,the angle being selected so that those two segments are rotatable relative to one another between a setting in which the parts of the centreline therein are aligned with one another and a setting in which the parts of the centreline therein include an acute angle.

2. An arm as claimed in claim 1, wherein the angle which each of the obliquely extending terminating planes of the at least two segments includes with the part of the centreline present in the respective segment lies in a range of less than 45 degrees and more than substantially 22 degrees.

3. An arm as claimed in claim 1 or claim 2, wherein the segments of the succession comprise a plurality of pairs of two adjacent segments rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment, wherein the angles at which the terminating planes of the segments extend obliquely to the respective parts of the centreline present in those segments are substantially identical for all the segments of that plurality.

4. An arm as claimed in any one of the preceding claims, wherein the segments of thesuccession comprise a plurality of pairs of two adjacent segments rotatable relative to one another each about an axis perpendicular to a terminating plane of the respective segment, wherein the angles at which the terminating planes of the segments extend obliquely to the respective parts of the centreline present in those segments are different for at least some of the segments of that plurality.

5. An arm as claimed in any one of the preceding claims, wherein at least one of the segments comprises two sections rotatable relative to one another about an axis coincident with the part of the centreline in that segment.

6. An arm as claimed in any one of the preceding claims, wherein at least one of the segments in the succession is rotatable about a first axis perpendicular to a first terminating plane thereof relative to a first adjacent one of the segments in the succession and about a second axis perpendicular to a second terminating plane thereof relative to a second adjacent one of the segments in the succession, wherein the first and second axes are angularly offset relative to one another about the part of the centreline present in the at least one of he segments.

7. An arm as claimed in any one of the preceding claims, wherein each terminating plane includes an acute angle and an obtuse angle with, respectively, two opposite sides of the part of the centreline present in the respective segment and defines a terminating face of that segment, the face and therewith the segment being truncated at the side of the centreline part with the obtuse angle.

8. An arm as claimed in any one of the preceding claims, wherein at least two of the segments are of respectively different dimensions in the directions of the parts of the centreline therein.

9. An arm as claimed in any one of the preceding claims, wherein the dimension of the arm transversely to the centreline reduces over the length of the arms between mutually opposite ends thereof.

10. An arm as claimed in any one of the preceding claims, wherein each of the segments has a substantially cylindrical circumferential surface between oblique terminating planes thereof.

11. An arm as claimed in any one of the preceding claims, wherein the fixing means is arranged to fix the segments in selectable rotational settings by a mechanically positive couple.

12. An arm as claimed in claim 11, wherein the mechanically positive couple is provided by a sliding detent system.

13. An arm as claimed in any one of claims 1 to 10, wherein the fixing means is arranged to fix the segments in selectable rotational settings by a friction couple.

14. An arm as claimed in any one of the preceding claims, comprising drive means accommodated in the segments and operable to selectably rotate each two adjacent segments in the succession relative to one another.

15. An arm as claimed in claim 14, wherein the fixing means is provided by the drive means in non-operating state.

16. An arm as claimed in claim 15, wherein the fixing means comprises an arresting brake co-operable with the drive means.

17. An arm as claimed in any one of the preceding claims, wherein the arm is provided at one of two mutually opposite the ends thereof with mounting means for mounting on a support.

18. An arm as claimed in claim 17, wherein the arm is provided at the other one of the two ends thereof with attaching means for attaching an implement, tool or other useful or utility article.A

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