NL2017167B1

NL2017167B1 - Robot arm

Info

Publication number: NL2017167B1
Application number: NL2017167A
Authority: NL
Inventors: Bastiaan Cornelis Van Dijk Archibald
Original assignee: Penta Robotics Patents B V
Priority date: 2016-07-14
Filing date: 2016-07-14
Publication date: 2018-01-18

Abstract

A robot arm comprising a base 3 supporting four actuators 5, four composite arms 25, 27, 29, 31 and a mobile platform 7. Said mobile platform 7 transmits torque from said actuators 5 to a tool holder 15. All composite arms having one end connected to one of the actuators 5 and the other end connected to said mobile platform 7. The mobile platform 7 consists of two parts 11 and 13. Part 11 has a pivot axis 9 which runs parallel to the plane of said base 3, carrying and enabling levers 13A and 13B of part 13 to swivel about said pivot-axis 9 transmitting torque to the tool holder 15.

Description

DESCRIPTION:

Technical filed of the invention

The invention relates to a robot arm which is capable of moving a tool in three orthogonal displacement directions and around an axis of rotation, comprising: - a base, - four actuators connected to said base, - a mobile platform comprising two parts which are connected to each other by means of a pivot axis and which are pivotable with respect to each other, as well as a rotatable tool holder, which is mounted in a first part of the two parts and to which a gear wheel is mounted which meshes with a gear ring of a crown wheel segment which is attached to a second part of the two parts and of which the center coincides with the pivot axis, - a parallel mechanism through which the mobile platform is connected to the actuators, comprising: - four composite arms, which each at one end are connected with one of the actuators, and with the other end are connected to the mobile platform, and each are composed of: - an arm portion wliich has one end connected to the corresponding actuator, and -- two parallel rods, wliich with one end are pivotally connected to the other end of the arm portion via a ball joint, and with the other end are pivotally connected to the mobile platform via a further ball joint, - wherein two of said aims which are in front of each other are connected to the first part of the mobile platform and the other two arms, which are also in front of each other are connected to the second part of the mobile platform.

Background of the invention

Such a robot arm is known from US 2012/0227532 A. The mobile platform of this known robot arm transmits torque from said actuators to the rotatable tool holder. To this end the mobile platform consists of two members. The first member comprises a pivot-axis enabling the second member to swivel about said pivot-axis and thereby transmitting torque to rotatable tool holder.

Summary of the invention

It is an object of the present invention to improve the known robot arm. To this end the robot arm according to the invention is characterized in that the second part of the mobile platform is made up of two separate levers which are connected to the first part of the mobile platform via the pivot axis, wherein each lever is connected to one of the arms and the crown wheel segment is attached to one of the levers and that a further crown wheel segment is attached to the other lever, and is also in engagement with the gear wheel which is mounted on the tool holder. To rotate the tool holder the two arms connected to the second part of the mobile platform have to move in the same direction. This in contradistinction with the arms of the known robot arm which have to move in opposite direction. Because the arms have to be moved in the same way it is easier to control the arms. Further when rotating the tool holder the forces exerted on the tool holder cancel each other out and only a torque is exerted on the tool holder, so that there is less load on the mobile platform and on the arms.

Preferably the pivot axis is at right angles to the tool holder and is parallel to an imaginary connecting line between the ball joints connecting the two parallel rods of one of the arms linked to the lever with this lever.

Brief description of the drawings

The invention will be further elucidated below on the basis of drawings. These drawings show an embodiment of the robot arm according to the present invention. In the drawings:

Figure 1 is a perspective view of a robot arm according to a preferred embodiment of the invention;

Figure 2 is a side view of a first embodiment of the mobile platform of the robot arm;

Figure 3 is a cross section of the mobile platform shown in figure 2;

Figure 4 is a perspective view of a second embodiment of the mobile platform with the levers of the second part of the mobile platform in one of the extreme positions;

Figure 5 is a perspective view of the mobile platform shown in figure 4 with the levers of the second part of the mobile platform in the other the extreme position; and

Figure 6 is a perspective view of a third embodiment of the mobile platform.

Detailed description of the drawings A robot arm 1 which is capable of moving a tool in three orthogonal displacement directions and around an axis of rotation can be observed in Figure 1. The robot arm comprises a base 3 with four actuators 5 connected to it. To each of these actuators a composite arm 25,27,29,31 is attached via one of its ends. The other end of each arm is connected to a mobile platform 7. The mobile platform is moved in the 3D working space of the robot arm by means of the composite arms, operated by the actuators 5.

The mobile platform 7 comprises two parts 11 and 13, which are connected to each other by means of a pivot axis 9 and which are pivotable with respect to each other.

The mobile platform further comprises a rotatable tool holder 15, which is mounted in a first part 11 of the mobile platform. A gear wheel 17 is mounted on the tool holder and meshes with two gear rings 19 of two crown wheel segments 21 which each are attached to a second part 13 of the mobile platform. The centers of the two gear rings coincides with the pivot axis 9.

The four composite arms are part of a parallel mechanism 23 through which the mobile platform 7 is connected to the actuators 5. Each composite arm is composed of an arm portion 33,35,37,39 which has one end connected to the corresponding actuator 5, and two parallel rods 41,43,45,47, which with one end 41a,43a,45a,47a are pivotally connected to the other end of the arm portion via a ball joint 49a-d,51a-d, and with the other end 41b,43b,45b,47b are pivotally connected to the mobile platform 7 via a further ball joint 53a-d, 55a-d.

Two of said arms 25,29 which are in front of each other are connected to the first part 11 of the mobile platform, and the other two arms 27,31, which are also in front of each other are connected to the second part 13 of the mobile platform.

The second part 13 of the mobile platform is made up of two separate levers 13A,13B which are connected to the first part 11 of the mobile platform 7 via the pivot axis 9. Each lever is connected to one of the arms 27,31 and the crown wheel segment 21 is attached to one of the levers 13A A further crown wheel segment 57 is attached to the other lever 13B, and is also in engagement with the gear wheel 17 mounted on the tool holder 15.

The pivot axis 9 is at right angles to the tool holder 15 and is parallel to an imaginary connecting line 59 through the ball joints 53b and 55b.

The actuators 5 are formed by motors with associated reduction gearboxes. The arm portions 33,35,37,39 are attached to drive shafts of the reduction gearboxes and are only able to pivot around one axis. The actuators 5 and the drive shafts are located in a plane, wherein the drive shafts of adjacent actuators are at an angle of 90 degrees with respect to each other.

The rods 41,43,45,47 together with the end of the arm portion 33,35,37,39 which is present between the ball joints 49a-d,51a-d, and together with the end of the lever 13A,13B of the second part which is present between the further ball joints 53a-d, 55a-d, constitute a parallelogram.

By controlling the four actuators 5, the tool holder 15 can be moved with retained orientation and inclination in a 3-D space with three translations and in addition one vertical rotation.

Figures 2 and 3 show that by controlling the four actuators 5, levers 13A and 13B of the mobile platform 7 can be swiveled about pivot axis 9. By inclining levers 13A and 13B in relation to part 11 torque is transmitted through the ring gear to the tool holder 15. Depending on the angle of inclination of levers 13A and 13B, a rotational angle of the tool holder can be achieved ranging from 0 to 360 degrees.

Figures 4 and 5 show a slightly different embodiment of the mobile platform 7A with the levers 13A and 13B in two extreme positions. All parts which are the same as those of the embodiment shown in figures 1-3 have the same reference signs.

Figure 6 shows a further slightly different embodiment of the mobile platform 7B. All parts which are the same as those of the embodiment shown in figures 1-3 have the same reference signs.

Although the present invention is elucidated above on the basis of the given drawings, it should be noted that this invention is not limited whatsoever to the embodiments shown in the drawings. The invention also extends to all embodiments deviating from the embodiments shown in the drawings within the context defined by the claims.

Claims

A robot arm (1) capable of moving a tool holder in three directions perpendicular to each other and rotating about one axis of rotation, comprising: - a base (3), - four actuators (5) connected to the base - a mobile platform (7) which comprises two parts (11,13) connected to each other via a hinge axis (9) and rotatable relative to each other, as well as a pivot axis (15) which in a first part (11) of both parts is mounted and to which is mounted a gear (17) in engagement with a gear ring (19) of a crown gear segment (21) attached to a second part (13) of the two parts and whose center coincides with the pivot axis ( 9), - a parallel mechanism (23) via which the mobile platform (7) is connected to the actuators (5), comprising: - four composite arms (25, 27, 29, 31), each connected to one end with one of the actuators (5) and with the other end connected to the mobile platform (7) and each composed of: - an arm part (33,35,37,39) connected at one end to the corresponding actuator (5), and - two parallel rods (41,43,45,47), each of which can be pivoted at one end be connected via a ball joint (49a-d, 51a-d) to the other end of the arm part (33,35,37,39) and be pivotable with the other end via a further ball joint (53a-d, 55a-d) connected to the mobile platform (7), wherein of these arms two opposite arms (25, 29) are connected to the first part (11) of the mobile platform and the two other arms (27, also opposite each other) 31) are connected to the second part (13) of the mobile platform, characterized in that the second part (13) of the mobile platform is composed of two separate levers (13A, 13B) which are connected via the pivot axis (9) connected to the first part (11) of the mobile platform (7), each handle being connected to one of the arms (27,31) and the crown The wheel segment (21) is attached to one of the levers (13A) and a further crown wheel segment (57) is attached to the other lever (13B) and is also engaged with the gear (17) attached to the pivot axis (15).

Robot arm (1) according to claim 1, characterized in that the pivot axis (9) is present perpendicular to the axis of rotation (15) and is parallel to an imaginary connecting line (59) between the ball joints (53b, 55b) parallel rods (41,43,45,47) of one of the arms connected to the handle (13A, 13B) connect to this handle.