Field of invention

The present invention relates to a wrist for an industrial robot, which wrist includes an inner wrist part and at least one manoeuvre connection means. The invention also relates to an industrial robot including such a wrist.

Background of invention

In an industrial robot that is intended to cooperate with human workers, special precautions must be taken to ensure safety. To this end, the robot may be equipped with a soft foam padding on its external surfaces. Furthermore it is desirable to conceal electric cabling, pneumatic tubing and other process cabling within the arm to prevent accidents due to entanglement. One way to achieve this is to use hollow-shaft motors and gears and route the cabling etc. through the axis of rotation of each joint. However, hollow-shaft transmission components are up to double the price of standard gears and motors.

An example of such an arrangement is disclosed in US 2008/0223170, having hollow arms and an internal cavity in the wrist for the cables and ducts.

US 5732599 discloses an industrial robot with hollow arms through which the electric cables extend. However, to avoid sharp bends in the cables and wires at the joint, the cables and wires exit from the interior of the arm shaft prior to the joint and are brought into the interior space of the other arm after passing over the joint section. At the joint the cable is protected by an external shroud.

JP2004090152 discloses a robot wrist having a wrist casing enclosing the wrist and the cables. The wrist includes hollow-shaft components through which the cables extend.

JP 7052074 discloses a robot wrist where the cables are located in a special wiring chamber at one side of the wrist.

US 2008/0315820 and US 2008/0148895 disclose further examples of robot wrists with internal cables.

Summary of invention

The object of the present invention is to provide a robot wrist with manoeuvre connection means such as cables and pneumatic tubes with an eliminated or at least reduced risk for these connection means to interfere with external objects or with the bearings, gears and similar parts of the inner part of the wrist, and also can be made at reasonable cost.

This object is achieved in that a robot wrist of the kind initially specified include the specific features that the inner wrist part includes solid-shaft

transmission components, which wrist further includes an outer shroud, and which manoeuvre connection means is arranged inside the outer shroud.

The outer shroud reduces the risk that the manoeuvre connection means will come into contact with humans or other external objects, which could entail the risk for accidents. Since the manoeuvre connection means are safe located inside the outer shroud it is not necessary to use hollow-shaft components in the wrist for protecting them Thus solid-shaft components are used which leads to a cost saving design.

The terms axial, tangential, eccentric and the like in the present

application relate to the extension of the axis around which the tool flange of the wrist is rotatable, if not otherwise explicitly stated.

According to a preferred embodiment, the wrist further includes a tool flange having a substantially planar portion that is perpendicular to the sixth axis and having a cylindrical wall that is concentric with this axis and projects into the outer shroud.

Arranging the tool flange in this way is advantageous with regards of the protection of the manoeuvre connection means at the area where they terminate from the wrist to be connected to the tool. Preferably, the cylindrical wall is smoothly fitted into the outer shroud so that they together form a continuous external shielding.

According to a further preferred embodiment, the manoeuvre connection means extend into the inside of the cylindrical wall.

This embodiment makes use of the advantage obtained with the cooperating outer shroud and the cylindrical wall.

According to a further preferred embodiment, the manoeuvre connection means includes at least one electric cabling and/or at least one pneumatic tubing. Since these are the most common means in this respect, the invention is of particular interest for such application. In most applications both an electric cabling and a pneumatic tubing are present. Other kinds of similar equipment might be present as well. Signalling wires and other controlling connections are also included in the term manoeuvring connection means.

According to a further preferred embodiment, the at least one manoeuvre connection means is completely concealed within the outer shroud. Thereby the protective function of the outer shroud is optimized.

According to a further preferred embodiment, the outer shroud includes soft padding. This further reduces the risk for accidents, should the wrist come into contact with a human or other external objects.

According to a further preferred embodiment, the wrist includes axis number six of the robot, and outer shroud is substantially cylindrical and concentric with this axis.

Normally the need for a protected arrangement of the manoeuvre connection means is most critical close to the tool operated by the robot, which implies that in most cases the sixth axis is included in the wrist. The concentric arrangement of the shroud around this axis is an advantageous adaption to the normal design of this wrist and to an optimized extension of the manoeuvre connection means at this wrist.

According to a further preferred embodiment, the outer shroud consists of two halves that are joined together in a median plane through the sixth axis.

Having the outer shroud divided into two halves in this way is

advantageous when assembling the wrist. It will also make it simple to demount the wrist, e.g. for maintenance, repair or adjustment.

According to a further preferred embodiment, each manoeuvre connection means forms at least one loop inside the outer shroud.

The loop in an advantageous way provides a possibility for the movements that are necessary for the manoeuvre connection means when the robot operates and there are rotational movements around the axes of the wrist. Since the loops are located within the space that is protected by the shroud, the movements in the loops do not risk causing any interference with other objects.

According to a further preferred embodiment, the manoeuvre connection means includes at least one electric cabling and at least one pneumatic tubing, arranged such that the electric cabling and the pneumatic tubing reach the tool flange in a tangential direction. According to a further preferred embodiment, the electric cabling extends about at least 90° along the inside of the cylindrical wall of the tool flange. This arrangement provides a good adaption for connecting the electric cabling from the spacing between the shrouds to a tangential direction thereof.

According to a further preferred embodiment, each manoeuvre connection means is attached to a lug arranged adjacent the end of the inner wrist part that is opposite to the tool flange. The fixation of the manoeuvre connection means in this way enables a controlled extension of these through the spacing between the shrouds towards the tool flange.

According to a further preferred embodiment, the electric cabling terminates in a connector, which connector is mounted on the tool flange. Thereby the conductors do not have to be individually attached to the poles of the electric connection with the tool, which can be very time consuming. When the conductor is attached to the connector it is just to attach the connector to the tool flange.

According to a further preferred embodiment, the connector is mounted in an eccentrically located recess on the front side of the tool flange. The recess allows a rapid mounting of the connector onto the tool flange, and the eccentric location provides an advantageous adaption to the drawing of the electric cabling in the spacing inside the outer shroud.

According to a further preferred embodiment the inner wrist part includes a casting enclosing gears and bearings, and the manoeuvre connection means extend between the casting and the outer shroud. By the casting the manoeuvre connection means are safely prevented from coming into contact with the bearings and the gears of the wrist, whereby the risk for damage due to contact with these elements is eliminated.

The invented robot provided with a wrist according to the present invention has advantages similar to those of the wrist, in particular to any of the preferred embodiments thereof, as have been described above. The above described preferred embodiments of the invention are specified in the dependent claims. It is to be understood that further preferred embodiments of course can be constituted by any possible combination of preferred embodiments above and by any possible combination of these and features mentioned in the description of examples below.

The invention will be further explained through the following detailed description of examples thereof and with reference to the accompanying drawings.

Short description of the drawings

Fig. 1 is a perspective view of a robot arm with a wrist according to the invention.

Fig. 2 is an exploded view in perspective of the wrist in fig. 1

Fig. 3 is a perspective view of details of fig. 2

Fig. 4 is a side view of the wrist in fig. 1 with parts removed.

Fig. 5 is an end view of fig. 4.

Fig. 6 is a schematic side view of an industrial robot according to the invention

Description of examples

Fig. 1 shows the lower arm 1 and of an industrial robot designed to work cooperatively with human workers. The arm 1 is connected to a wrist 2 with a tool flange 5 for a robot tool (not shown). The figure shows the three final axes of rotation, the fourth axis A, the fifth axis B, and the sixth axis C. The gears and motors for axes five and six are housed within an encapsulated module 3, which is partially encased in soft padding 4. On the front side of the tool flange 5 there are connection means for control and power supply to the tool that is to be mounted on thereon. The connection means includes an outlet 24 for pneumatic tubing and a connector 23 for electric connection to the tool. The connector 23 is connected to cabling drawn through the wrist 2.

In the perspective exploded view of fig. 2 the main parts of the wrist 2, namely the inner part 6 thereof, a first half 8a of an outer shroud, a second half 8b of the outer shroud and the tool flange 5. The outer shroud parts 8a, 8b are shown with the padding removed. The inner part 6 of the wrist 2 has a casting 9 which houses the bearings and gears for the fifth and sixth axes. At the left side of the casting 9 the motor 10 for the fifth axis is mounted. The motor 1 1 for the sixth axis can be seen on the rear side of the casting 9. A pneumatic tubing 12 having a loop 14 extends from the rear side of the inner wrist part 6 to the front side thereof for connection to a tool that is to be mounted on the tool flange 5. From the rear side also an electric cabling 13 with a loop 15 extends to the side of the tool flange 5. The electric cabling includes a plurality of conductors 7. The pneumatic tubing 12 and the electric cabling 13 terminate in the tangential direction with respect to the sixth axis, and are tangentially directed for about 90° at their ends.

When the parts seen in fig. 2 are assembled the pneumatic tubing 12 and the electric cabling 13 are located outside the casting 9. The tool flange 5 has a cylindrical wall 16 in the rearward direction. With the tool flange attached to the inner wrist part 6, the cylindrical wall thereof is located radially outside the casting 9 and radially outside the pneumatic tubing 12 and the electric cabling 13. The tangentially directed part of the pneumatic tubing 12 and the electric cabling 13 thereby extend along the inside of that cylindrical wall 16. The outer shroud halves 8a, 8b are mounted to each other and enclose the pneumatic tubing 12 and the electric cabling 13 as well as the fifth axis motor 10. The front end of the outer shroud 8a, 8b extends on the outside of the cylindrical wall 16 of the tool flange 5.

On the front side of the tool flange 5 there is a connector 23 at which the electric cabling 13 terminates and through which electric connection to a tool is established. Also on the front side of the tool flange is a connection device 24 at which the pneumatic tubing terminates and this is for the air supply to the tool.

The connector 23 is an insert that is mounted in an eccentric recess on the front side of the tool flange 5.

In fig. 3 the rear side of the casting 9 can be seen. From this side a lower 17 and an upper 18 lug protrude. The lower lug 17 provides both anchoring point for two electrical connectors 20 and fixation for the two halves 8a, 8b of the outer shroud. The connectors on the lower lug 17 are for motor phase and ground cables (not shown). The upper lug 18 provides fixation for two further connectors 19 and fixation by means of cable tie 21 of the pneumatic tubing 12 and electric cabling 13. On the upper lug 18 also connectors for the motor position sensor cables (not shown) are provided. From the upper lug 18, the pneumatic tubing 12 and the electric cabling 13 depart in the same direction. This is most clearly seen in fig. 4 and 5. The pneumatic tubing 12 and the electric cabling 13 occupy the annular volume between the casting 9 and the outer shroud 8a, 8b before terminating at the tool flange 5. Sufficient slack is introduced so that the pneumatic tubing 12 and the electric cabling each form a loop 14, 15. The slack length is such that except at the extremes of travel, the pneumatic tubing 12 and the electric cabling 13 never collide with each other. The electric cabling terminates tangentially at the tool flange 5 and hence its cable loop forms a so called "rolling bend" during rotation of axis six. A similar motion is achieved for the pneumatic tubing 12 which also terminates tangentially. Using the dual rolling bends, a total tool flange rotation of just over 360°is attained.

The cylindrical wall 16 which protrudes rearwards from the tool flange 2 has the purpose to contain the loops 14, 15 of the pneumatic tubing 12 and the electric cabling 13. The cylindrical wall 16 prevents them from buckling when the tool flange 5 is reversed from maximum rotation position. Without the cylindrical wall, the rolling bend of the electric cable would be unable to reverse successfully from a position of maximum excursion. This is due to the fact that as it is drawn past a constriction that is formed at the neck 22 of the casting 9, the rolling bend loop is forced flat against the tool flange 5. Upon reversal from maximum excursion the flat loop expands radially and a portion makes contact with the outer shroud wall 8a, 8b. The friction this point encounter causes it to resist rotation so the trailing portion of the loop buckles. By contrast, when the cylindrical wall 16 of the tool flange 5 is in place, the radially expanding loop meets a surface which is moving with the tool flange 5 so the whole loop can be reversed past the constriction of the neck 22 of the casting 9 without buckling.

Fig. 6 illustrates an industrial robot 101 having a lower arm 1 with a wrist 2 according to the present invention.