Metal working – Plural diverse manufacturing apparatus including means for... – Common reciprocating support for spaced tools
Patent
1989-08-01
1990-12-25
Briggs, William
Metal working
Plural diverse manufacturing apparatus including means for...
Common reciprocating support for spaced tools
B23Q 3155
Patent
active
049792849
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for changing a sensing device in a positioning machine, such as a coordinate measuring machine, machine tool or inspection robot. Such apparatus is known, and comprises:
a magazine having means for releasably supporting the sensing device in a stored position;
a holder which is capable of translational movement by the positioning machine, relative to the magazine and to a workpiece, for removal of the sensing device from the magazine, performance of a sensing operation on the workpiece, and return of the sensing device to the magazine;
means for releasably coupling the sensing device to the holder, comprising first support elements provided on the holder, second support elements provided on the sensing device and engageable with the first support elements, and releasable bias means for urging the first and second support elements into engagement with each other; and
means for actuating the coupling means between a coupled state (in which the bias means urge the first and second support elements into engagement with each other) and an uncoupled state (in which the bias means are released and the holder is separated from the sensing device with the sensing device supported in the magazine) in order to couple and uncouple the sensing device and the holder.
In the known apparatus, the actuating means has a separate operating means, located either in the holder or in the magazine.
For example, in GB 2047133 (Renishaw), the coupling means is in the form of a bayonet joint, and the holder includes a motor for rotating the holder relative to the sensing device stored in the magazine, in order to actuate the bayonet joint. In U.S. Pat. No. 4649623 (Zeiss), the coupling means includes an electromagnet in the holder, which forms part of the bias means for urging the first and second support elements into engagement. Both these known arrangements thus require an operating means (a motor or electromagnet) in the holder. There is a difficulty in making the necessary electrical connections to such an operating means in the holder, bearing in mind that the holder is movable. Furthermore, the operating means increases the mass of the holder, so that the positioning machine is more subject to inertial deflections when the holder is accelerated Since such deflections reduce the accuracy of measurement, the mass of the holder is one of the limiting factors on the speed at which measurements can be made.
In EP 0142373 (Renishaw), on the other hand, such problems are overcome by providing the operating means within the magazine itself The magazine includes a screwdriver-type operating member, driven by a motor, which engages and operates the coupling means when the holder picks up or puts down a sensing device in the magazine However, this results in a more complicated and expensive magazine, and the need to ensure correct operating engagement between the screwdriver and the coupling means.
In one aspect, the present invention is characterised in that the actuating means is operable by the relative translational movement between the holder and the magazine. Such relative translational movement is in any case an operational requirement in a positioning machine, and therefore the preferred embodiments of the present invention do not require any separate motor or electromagnet in the holder or in the magazine.
Preferred embodiments of the invention will now be described with reference
to the accompanying drawings, wherein: FIG. 1 is an elevation of a positioning machine including the connecting mechanisms FIG. 2 is a view on the line II--II in FIG. 1. FIG. 3 is an enlarged detail of FIG. 2. FIG. 4 is a section on the line IV--IV in FIG. 3. FIG. 5 is a section on the line V--V in FIG. 3. FIG. 6 is a view similar to FIG. 4 but shows a first modification. FIG. 7 is a section on the line VII--VII in FIG. 6 and shows different operational positions. FIG. 8 is view similar to FIG. 6 but shows a second modification and shows a first operational position. FIG. 9 is a section on the line IX--IX in FIG
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Lewis Richard H.
McMurtry David R.
Wells Peter J.
Briggs William
Renishaw plc
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