Compact manipulation robot

A parallel-type displacement device having at least three arms each pivoting about a pivot axis, the pivot axes defining a polygon as seen from a point above the device, wherein each of the arms is actuated by an actuator and each of the arms is further connected to a head defining a small base through linking members respectively articulated on the head and the arm, each said arm and its respective head forming a hinge having two degrees of freedom such that the head always maintains its position and orientation, and in which in a neutral position, each arm is arranged so that, if drawing from the geometrical center of the polygon a straight line that is parallel to the pivot axis of any one of the arms, the straight line intersects that arm.

FIELD OF THE INVENTION

The invention relates to a device for displacing an object in space.

BACKGROUND

To move an object in space, manipulation arms are known, the articulations of which are mounted in series and those the articulations of which are mounted in parallel. These arms are also called robots.

The robots of these serial articulation types have a disadvantage in that they are relatively heavy and thus have a high inertia which prevents them from working at high rates.

The so-called parallel robots enable much faster displacements but the amplitude of the movements is limited.

The invention relates to a so-called parallel robot.

Such robots are more particularly known from EP-A-250 470, EP-A 1.129.829, WO-A-0035640 including three actuators, including a fixed part and a movable part having only one degree of freedom with respect to the fixed part, with each movable part being connected to a movable head through linking members.

The device is shaped as a deformable pyramid with triangular bases.

Each actuator is an electric motor the rotation axis of which is coupled to an arm (the movable part) pivoting about the actuator rotation axis.

The private axes of the arms form a triangle and the linking members are respectively hinged on a head (the small base) and the corresponding movable part.

The articulations of such linking members to the arms as well as to the head are given two degrees of freedom.

Then, the orientation and the direction of the head are not modified in space.

Often, a telescopic transmission gripping device is mounted at the centre of the system.

A central support carries the actuators. This central support substantially has the same dimensions as defined by the three pivoting axes.

The rotation bearings of the pivoting arms are saddled on the pivot axes and are, each, half inscribed in the surface defined by the pivoting axes of the arms.

The arms are radial, at least in their end parts, and extend to the outside of the central support. The displacement amplitude is minimised by the extent of the support which must have a sufficient size to carry the actuators and often a fourth arm which is used as a gripping device connecting the larger base to the smaller base. The displacement amplitude is related to the useful length of the arm.

The overall dimensions are defined by the circle going through the ends of the arms when the system is in neutral position and the arms are then in the same plane, here a horizontal plane.

The axes of the arms are generally mounted so that the longitudinal axes of said arms intersect at the centre of the triangle formed by the pivot axes.

It should be understood that the larger the support for given overall dimensions, the smaller the length of the arms. Thus for the overall dimension of approximately 550 millimeters in radius, the length of the arm is 350 millimeters, the working height obtained is thus of the order of 300 millimeters and the diameter of the working area is of the order of 1,100 millimeters.

To increase the length of the arms for given overall dimensions, the size of the support should be reduced but it depends on the size of the actuators and in the configurations known, it cannot be much reduced.

Now, the overall dimensions must also be a factor taken into account for positioning said robots. In addition, reducing the size support also means for some of the possible positions of the arms, reducing the rigidity of all the movable members of the robot. Such constraints result in the present definition of the state of the art which is composed of parallel robots having a large fixed base and having arms radiating to the outside.

SUMMARY

The invention provides a device which is more compact.

For this purpose, the invention relates to a parallel-type displacement device including at least three arms each pivoting about a pivot axis, the pivot axes defining a polygon as seen from above, wherein each of the arm is actuated by an actuator and each of the arms is further connected to a head defining a small base through linking members respectively articulated on the head and the arms, the hinges having two degrees of freedom and the head always maintaining its position and orientation, this device being characterised in that in the so-called neutral position, each arm is arranged so that, if drawing from the geometrical centre of the polygon a straight line that is parallel to the pivot axis of any of the arms, such straight line intersects the arm considered.

DETAILED DESCRIPTION

While referring to the drawing, a device1for displacing objects of the parallel-type can be seen.

This device makes it possible to displace objects at a high rate.

Conventionally, the device includes at least three arms2pivoting each about a pivot axis3.

The pivot axis are either inclined with respect to a plane parallel to a head working plane. Generally, when the axes are inclined, they are shaped like a Chinese hat, the summit of which is directed upwards, but the tip oriented downwards is possible and has no effect on the invention.

As seen from above, the pivot axes or the projections thereof in a plane parallel to the head working plane form the sides of a polygon such as a triangle for three arms and a square or a rectangle for four arms.

The arms2are rectilinear or not rectilinear (FIG. 8).

For a better understanding the following description was written while considering that the private axes are in a horizontal plane.

An actuator4is at least indirectly engaged on one of the two ends of each pivoting arms, with each of these arms2being further linked to a head5through linking members6which are respectively articulated to the head and to the arm. These hinges60have two degrees of freedom.

The parallel-type displacement device is shaped like a kind of truncated pyramid which is deformable and has a large polygonal base including at least three arms2pivoting each about a pivot axis3guided in rotation on at least a bearing7, each arm being actuated by an actuator4and each of these arms being further linked to a head5forming the small base through linking members6respectively articulated to the head and to the arm with two degrees of freedom, the head always keeping its orientation and direction.

In a so-called neutral position, the head is positioned above the projected surface and all the arms are horizontal which means parallel to a head working plane. The head working planes are parallel and non-concentric.

According to one characteristic feature, each arm is positioned so that it is possible from the geometrical centre of the polygon P to draw a ray parallel to the pivoting axis of any of the arms, with said line intersecting the considered arm.

The longitudinal axes of the arms form a triangle for a three arm configuration or for example a square (FIG. 9) when four arms are provided. The arms can be longer or shorter than the polygon sides.

This configuration of the arms can be seen when the arms are substantially in a plane parallel to the head working plane.

As a matter of fact, when the arms are closed to the vertical, the parallel line cannot intersect the arm.

As can be seen, the actuators are mounted either outside the exemplary polygon inFIG. 2or at least partially inside said exemplary polygon inFIG. 3. They can be positioned out of the plane intersecting this polygon.

When comparingFIG. 1of the prior art andFIG. 2which is that showing the new position of the arms, a difference appears in the overall dimensions.

The robots inFIG. 1andFIG. 2are substantially on the same working area in x, y, z but the robot ofFIG. 2is more compact.

InFIG. 1, the overall dimensions are shown by circle C1which has been reproduced inFIG. 2. It can be seen that for arms having the same length the overall dimensions are more reduced in the embodiment of the invention.

It can also be seen that such overall dimensions can be reduced again if the actuators are positioned inside the triangle defined by the longitudinal axes of the arms.

In the example ofFIG. 15, transversal parts80linking the two lower articulation points of the linking members to the head are positioned radially with respect to the head.

In the versions ofFIGS. 14 and 16, the longitudinal axes of these transversal parts define a triangle.

InFIG. 14, the fastening point of the transversal parts is at the apex of the triangle whereas forFIG. 16the fastening point is positioned in the middle of the triangle side. The axes of these transversal parts can be parallel or inclined with respect to the head working plane5.

In some alternative solutions the linking members can be rectilinear, but in other solutions, they can be bent or S-shaped. Advantageously, ball sockets60made of ceramic will be used at the articulation points with the linking members. It can be useful to provide the ball sockets with an overpressure device and the bearings with sealing devices in dusty or moist environments in order to prevent them from being soiled or damaged.

Considering the very heavy accelerations which can be imparted by the operator, it can also be useful to double the fastening points of the linking members with safety cables or any other element of the same utilisation. The linking members can have a round, oval or polygonal section with simple or assembled wires.

It can be seen that the device includes a gripping device10with a telescopic transmission. This gripping device is mounted at the centre thereof (the centre of the three side pyramid when the latter is at its zero point, with the arms being in the same plane as the pivoting axes).

The gripping device is guided in rotation on the head of the device.

An additional actuator can have the gripping device rotate about its longitudinal axis.

The gripping device may be provided with a suction cup, claws or any other means for gripping an object.

The gripping device often has a variable length between two fixed points, i.e. the end hinges and it is also composed of an actuator, a high hinge, a telescopic transmission (two rods sliding one into the other), a lower hinge (a cardan or a ball socket) positioned on the head and a gripping member.

Advantageously, the upper hinge is positioned above the plane A containing the arms when these are in a horizontal position. This means, with respect to the plane A, that it is positioned in the space opposite that containing the head. Or the plane A is positioned between the upper hinge and the head.

The actuators are for example, electric motors known as “brushless” motors but these could be different means. They can be mounted at the end of the axis but a transmission through a toothed belt or any other belt makes it possible to position them in a different plane.

This gripping device can be connected to its actuator not by a telescopic transmission but by a parallel kinematic link (FIG. 10-11) with a gear reduction system, or by a cable control and a gear reduction system.

The actuator of this gripping device can also be directly mounted on the head but then the weight is increased and so is inertia.

As can be seen, one of the advantages of this device is that it is compact with respect to its working area. Just refer toFIGS. 12 and 13to compare the overall dimensions on a production line.

This compact characteristic makes it possible to provide the robots with many tools and can even result in robot matrices inFIG. 12.

When keeping in mind that for “pick & place” applications for the packaging of manufactured products, one travel of the robot out of two is generally carried out unloaded, all the interest of providing the robots as close to each other as possible clearly appears, which gives at certain points of the space the superposition of their respective working areas. A system for managing the thus obtained robot group will enable all the robots to work together in harmony and without bumps.

It should be noted that inFIG. 4or8the bearings7of the actuators are positioned outside the polygon formed by the pivoting axes.

FIG. 17shows an exemplary support100on which the motors4and the arms2supporting the long members6are mounted.

FIG. 17shows a robot provided with a gripping device10which is different from that shown for example inFIG. 7.

It is composed of an element10A having a non variable length and connected to the head5through a hinge200, for example of the cardan type. This member10A has its free end slidingly engaged in an articulated guiding mean10B which it goes through.

This free end10C is not immobilised at a fixed point, it is free to move in space.

This guiding means is for example composed in concentric rings.

FIG. 18or19shows in the upper part of the drawings the rings as seen from above and mounted with the axes120and121and in the lower part the non mounted rings.

An internal ring110articulated about the diameter axis120of a second ring111which is itself articulated about a diameter of axis121at 90° from the previous one on an external ring112which is indirectly or directly used as a driving ring. A cut is provided in the support100for the passage of the long member10A. This long member10A is locked in rotation in the internal ring110.

The guiding means is not very thick (FIG. 18) or the internal ring is extended by a liner114towards the head5which increases the guiding length (FIGS. 17 and 19).

The rings can be replaced by some kind of ball socket.

The robots are often shown hanging but they can be mounted on a support or even on a vehicle such as a trailer or a manipulation instrument and work in a plane perpendicular to the ground.