Tool changing – With means to condition or adjust tool or tool support
Patent
1996-06-12
1998-05-19
Pitts, A. L.
Tool changing
With means to condition or adjust tool or tool support
483 1, 483 30, 483 35, 409232, 901 41, B23Q 3155
Patent
active
057529043
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for an automatic tool change and an apparatus carrying Out the method. More precisely, the present invention relates to a method and an apparatus used in connection with an automatic change of rotating tools of robots or similar devices.
It is prior known to use various rotating tools in machining operations performed by a robot, the operations being such as drilling, grinding or burring. The arm of said robot is provided with drive means, e.g. with a pneumatically or hydraulically operated motor, said drive means being provided with a tool secured to a rotatable axis or shaft of said motor. It has been known to use commercially available tool holding systems, e.g. quick-release taper shanks, which are prior known by the man skilled in the art for the clamping of said tool to said rotatable axis. However, in spite of the all-round operations of a robot, the tool change has been in general performed manually. This is due to several reasons, among others, since the robots generally in use are not able to carry and accurately move particularly heavy loads in the end of the arm thereof and therefore the rotating devices used are made as simple and light-weighted as possible. Thus the automatically operating tool holding and tightening devices used in normal machine tools, such as lathes, are too big in size, complicated and heavy to be used in the robot applications. Furthermore, said rotating tools require one further axis of movement, i.e. rotation, which cannot be provided to the end of a robot arm in the same manner as it is arranged in said machine tools, since the free three-dimensional movements of said robot prevent the providing of the rotating torque by similar mechanical means as those used, for example, in said lathes for providing the rotational movement. Adding one further axis of movement and a programmed indexing of an angular position of said axis to the control means of a robot is difficult and in use the programming work would be too difficult and time-consuming to be economically profitable.
DE-patent 3208621 discloses one solution for the automatic clamping of a tool. The apparatus comprises a clamping nut provided about the tool holder provided in the axis of said robot. Said tool, provided with a parallel shank is disposed through said nut and said nut is tightened by a cooperation of a special toothed rack which is driven by a work cylinder and a support means driven by a further work cylinder. A significant disadvantage of the arrangement disclosed in said publication is, however, that only tools with parallel shanks can be used, since the angular position (i.e. the rotational position) of the part of said robot receiving said tool is not known. This results in an insufficient ability of transferring the power required in modern machining appliances. Furthermore, only tools having equal shank diameters can be used in the arrangement disclosed in said DE-publication.
The use of an arrangement according to said DE-publication is also difficult because of the relatively big size of said tightening nut, which makes the working of the robot more difficult. Furthermore, the total equipment disclosed is very space consuming in the movement range of the robot. The arrangement is also very complicated and it comprises numerous parts which require very precise manufacturing and which parts are easily blocked-up by the chips generated during the machining process and the dirt present in work shops or similar environments. This easily results in the jamming of said parts. Furthermore, it has been found difficult to control the correct tightening force of said clamping nut of said tool by the device disclosed in said publication and comprising a pneumatic or hydraulic work cylinder, In many cases there is also a significant disadvantage in that the exact rotational position of the tool is not known when initiating the machining process or in that the angular position of said tool cannot be automatically indexed to a predetermined position.
Thus, the rotatin
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Irri Oy
Kirkman Christopher
Pitts A. L.
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