Tool changing – Process
Reexamination Certificate
2000-01-12
2001-06-05
Briggs, William (Department: 3722)
Tool changing
Process
C211S001540, C483S054000, C483S058000, C483S059000
Reexamination Certificate
active
06241645
ABSTRACT:
The present invention relates to the changing of operating modules, such as probes, tool units or end effectors, on a coordinate positioning machine, such as a coordinate measuring machine, a machine tool, or a robot.
In our co-pending International patent application PCT/GB99/01215 we disclosed a system in which operating modules in the form of tool units are releasably coupled to the spindle of a machine tool by means of frictional engagement between the shank of the tool and the interior wall of a cavity within a chuck mounted on the spindle. In this disclosure, frictional engagement between the tool shank and the cavity wall is controlled by varying the hydraulic pressure within fluid chambers located within the chuck adjacent the cavity wall, causing the cavity wall to deflect elastically and grip or release the tool as appropriate. In accordance with this disclosure, other methods of controlling the frictional engagement between the cavity wall and the tool shank to retain a tool unit releasably within a chuck are contemplated, such as shrink-fitting by means of rapid and temporary localised heating of the chuck to allow insertion of the tool shank within the chuck, followed by rapid cooling of the chuck to cause the cavity wall to grip the tool shank as it contracts.
Tool-changing systems of the type disclosed in PCT/GB99/01215 have the advantage that the both the tool units and the chucks are light, and have a relatively simple construction. All of the relatively heavy connectors and/or other mechanical interfaces which are traditionally part of the tool unit, such as collets, taper shanks and pull-up studs, are dispensed with, along with the mechanisms which retract the tool units within the chuck during tool changing, and then retain them within the chuck during machining. This reduction in the mass carried by the spindle during machining is particularly significant on machine tools where the spindle is driven relative to stationary workpieces.
However, a requisite of such an improved tool changing system is that the clearance between the tool shank and the chuck cavity wall must be relatively small when the chuck is in its “open” state, i.e. the cavity wall is in a condition to receive the tool shank (for example by virtue of instant heating in the shrink-fit chuck system, or low hydraulic pressure in the hydraulic system). In some systems the clearance is as small as 10 microns. As a result of this requirement, relatively precise alignment of the chuck and the tool is required during tool changing.
A first aspect of the present invention provides a magazine for storing operating modules on a coordinate positioning machine to enable automated exchange of one operating module for another, the magazine having a base, by means of which it may be mounted to the machine, and at east one storage port containing an operating module, the storage port being mounted to the base by a compliant mount which provides at least two degrees of rotational freedom of the storage port relative to the base of the magazine, thereby to enable the operating module within the storage port to adopt the attitude required to enable its insertion in the chuck cavity during an exchange of operating modules. Preferably, the compliant mount permits motion of the storage port relative to the base with two rotational and two translational degrees of freedom.
In one embodiment of magazine, the storage port is supported on the base of the magazine by a pair of serially mounted gimbals, such as ball joints, for example.
In order to achieve the requisite alignment of the operating module within the storage port, and the chuck on the coordinate positioning machine, a further independent aspect of the invention provides mutually engageable alignment surfaces connected to the chuck and the storage port, engagement of which as the chuck and the storage port approach during an exchange operation will automatically cause the operating module within the storage port and the chuck cavity to attain alignment by virtue of the relative motion between the storage port and the base of the magazine permitted by the compliant mount.
Preferably, two pairs of mutually engageable alignment surfaces are provided, wherein a first pair are mutually engageable to provide a first and relatively coarse degree of alignment between the operating module and the chuck cavity, and a second pair of surfaces which are mutually engageable subsequent to engagement of the first pair of surfaces to provide a second and relatively fine degree of alignment between the operating module and the chuck cavity. In one embodiment, a pair of alignment surfaces are provided by surfaces on the storage port and the exterior of the chuck, while in a further embodiment a pair of surfaces is provided by a surface on the operating module and a surface at the mouth of the chuck cavity. In a further embodiment, both pairs of surfaces are on the storage port and the chuck, and in yet a further embodiment a single alignment surface serves as an alignment surface of both the first and the second pair of alignment surfaces.
Yet a further independent aspect of the present invention provides a method of operating a coordinate positioning machine having a chuck supported on one relatively moveable part of the machine which has a cavity within which an operating module may be releasably retained, and a magazine supported on a further relatively moveable part of the machine having at least one storage port containing an operating module, the method comprising the steps of: operating the machine to cause the magazine and chuck to approach, and during the approach, engaging mutually engageable alignment surfaces on the chuck and the storage port;
allowing the storage port to move relative to the one relatively moveable part of the machine as a result of forces exerted by engagement of the alignment surfaces during the approach, thereby to bring the operating module and the chuck into a predetermined alignment;
operating the machine to move the first and second relatively moveable parts to insert the operating module within the cavity;
subsequent to the insertion of the operating module within the cavity, causing the cavity wall to grip the operating module and thereby retain the operating module within the chuck by virtue of frictional engagement between the operating module and the cavity wall; and
with the operating module retained within the chuck, operating the machine to move the first and second relatively moveable parts to remove the operating module from the storage port.
In the foregoing description, reference has been made to the general applicability of the invention to all forms of coordinate positioning machine, and all types of operating module. Subsequent exemplification of the invention will be by reference to its applicability in relation to the field of tool changing on a machine tool, however no derogation from the general applicability of the invention is intended by this.
REFERENCES:
patent: 3191260 (1965-06-01), Jorgensen
patent: 4050837 (1977-09-01), Shichida et al.
patent: 4069918 (1978-01-01), Inoue et al.
patent: 4831721 (1989-05-01), Hirai et al.
patent: 5201696 (1993-04-01), Kinback et al.
patent: 0 060 638 A2 (1982-09-01), None
patent: 2555927 (1985-06-01), None
patent: 52-10981 (1977-01-01), None
patent: 8905210 (1989-06-01), None
patent: WO 99/56901 (1999-11-01), None
Briggs William
Oliff & Berridg,e PLC
Renishaw plc
LandOfFree
Method and apparatus for changing operating modules does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for changing operating modules, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for changing operating modules will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2522810