Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Reexamination Certificate
2002-09-26
2004-07-27
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
C074S490030, C901S016000, C901S023000, C901S028000
Reexamination Certificate
active
06766711
ABSTRACT:
TECHNICAL AREA
The present invention concerns an industrial robot according to the delta concept with an arm system. The present invention also relates to an application of a telescopic shaft for an industrial robot according to the delta concept. The present invention also relates to a method for an industrial robot according to the delta concept with an arm system intended for rotation in space.
THE PRIOR ART
The use of industrial robots for flexible automation of processes within industry has become ever more common in order to replace time-consuming, monotonous and difficult tasks. One such task, for example, could be the sorting of chocolate pieces or similar objects from a conveyor belt to predetermined places in, for example, cartons, where the objects move on a separate conveyor belt, at a certain speed. In general, the ability to handle small and fragile objects efficiently with high precision and at high speed is in heavy demand for the automation of industrial processes. An industrial robot for this application, among other applications, has been constructed according to what is known as the “delta concept”. This type of robot, known as a “delta robot”, can, for example, be placed into a frame construction over a conveyor belt, and has an arm system and a tool attached to it that is intended for rotation in space, that is, a rotation with three degrees of freedom along the x, y and z directions. The rotation of the robot arm described hereunder is intended to describe the performance of a rotational movement by the robot arm. The arm system normally comprises a base section and a movable plate and there between three arms formed from a number of jointed struts. The movable plate that is connected to the struts is moved parallel to the base plate, whereby the movable plate always has the same orientation and tilt as the base plate. This is important for the orientation of a gripping means that is connected to the movable plate. It is principally the struts that bear the load. A telescopic shaft, also known as a “fourth shaft”, is arranged between the base section and the movable plate. The function of this shaft is to work as a driving shaft from a motor in the base section to a tool connected to the movable plate. The rotation must have minimal play and it must be possible to carry out the rotation in space, that is, the distance from the movable plate to the base of the robot, the base section, is variable. The linear motion may have a speed of up to 10 m/s. The number of pick-ups of objects can be 120 per minute, which is equivalent to two objects per second. Furthermore, this delta robot is usually equipped with a system that visually identifies the objects and only selects those that are perfect.
One problem with this robot is that friction and play between component parts arise during rotational movements with the arm system. At the same time as the telescopic shaft is to increase/decrease in length, it must also be able to transfer relatively large torques with high precision, at high speed/acceleration, independently of whether the objects that are to be picked up are placed on a conveyor belt, randomly or placed in determined positions. On known telescopic shafts for industrial robots according to the delta concept, an inner shaft is stored in an outer tube with an ordinary sliding bearing, in the form of, for example, “splines” or similar means. This gives play in the transfer of torque and it cannot cope with a higher torque than 0.5 Nm at moderate speeds.
Industrial robots according to the delta concept are used in, for example, the foodstuffs industry, medical science, and in other areas in which environmental and health controls are very strict. The requirements for cleanliness on all process equipment in these sensitive environments are high. One problem with the use of an ordinary telescopic shaft, that is, of the general type in which an inner shaft is stored in an outer tube that is longitudinally displaceable, is that there are spaces that are difficult to clean where dirt and bacterial can easily congregate. An ordinary telescopic shaft, comprising, among other things, bearings and bushes, is also sensitive for cleaning such as rinsing with water.
An industrial robot according to the delta concept with an arm system is previously known through U.S. Pat. No. 4,976,582, which robot comprises a telescopic shaft. This patent document generally describes one so-called “delta robot”, which has an arm system and a tool connected to it that is intended for rotation in space, that is, a rotation with three degrees of freedom along the x, y and z directions. The arm system comprises a base section, a movable plate, and several jointed struts between the base section and the plate.
DESCRIPTION OF THE INVENTION
The present invention aims to achieve a device for an industrial robot, which device allows cleaning with water, is simpler to clean than conventional constructions and has minimal spaces in which dirt and bacteria can congregate. A further aim of the invention is to allow play-free displaceable torque transfering motions with low friction for a telescopic arm on such a robot. One aim of the present invention is thus to be able to carry out with an arm system for an industrial robot a rotational movement that is free of play in space, with minimal friction and with maximal stiffness. The rotational movement is to be possible at high speeds and accelerations, and with relatively large torques.
The solution is achieved with an industrial robot having the characteristics given in claim
1
. To be more precise, the present invention concerns according to claim
1
an industrial robot according to the delta concept with an arm system intended for rotation in space, which arm system comprises a base section, a movable plate, several jointed struts and a telescopic shaft arranged between the base section and the movable plate. Opposite ends of the struts and the telescopic shaft are connected to the base section and the movable plate, respectively. The telescopic shaft comprises a first telescopic arm and a second telescopic arm, which arms are arranged longitudinally displaceable relative to each other. The first telescopic arm comprises at least two rods, one inner holder to which the inner ends of the rods are fixed attached, and one outer holder, to which the outer ends of the rods are fixed attached. The second telescopic arm comprises at least two rods, one inner holder to which the inner ends of the rods are fixed attached, and one outer holder, to which the outer ends of the rods are fixed attached. The inner holder of the first telescopic arm comprises slots in which the rods of the second telescopic arm run. The inner holder of the second telescopic arm comprises slots in which the rods of the first telescopic arm run.
One advantage of the present invention is that it can be easily and rapidly cleaned independently of its position (rinsed with water), since the telescopic arm comprises easily accessible spaces and components that are not damaged by cleaning. At the same time, a very torsionally stiff construction is achieved, in which a telescopic shaft with play-free parallel movement that transfers torque and has low friction is obtained. The construction copes with high torques, greater than 1 Nm, and linear speeds up to 10 m/s. A further advantage is that friction and play are minimised, whereby the robot can carry out rotational movements at high speed and with high precision.
The telescopic shaft is arranged to carry out a rotational movement. The rods are arranged eccentrically, and they are displaced parallel at the telescopic arms relative to the rotation axis of the telescopic shaft, which means that the load on bearings is lower than that in an ordinary telescopic arm (in which an outer tube is stored in an inner shaft that is longitudinally displaceable within the outer tube). The reduced load according to the present invention depends on the transfer of the forces out to the eccentrically arranged rods, compared to an ordinary telescop
Hvittfeldt Håkan
Mikaelsson Pierre
ABB AB
Fenstermacher David
Franklin Eric J.
Venable LLP
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