Geometrical instruments – Gauge – Work support
Patent
1990-10-05
1992-06-30
Haroian, Harry N.
Geometrical instruments
Gauge
Work support
33 1AA, 33503, G01B 503
Patent
active
051251639
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a guideway support base for use with high accuracy measuring and checking machines.
BACKGROUND ART
Heretofore for purposes of accuracy, it has been necessary to construct co-ordinate measuring machines using heavyweight material such as granite, i.e. material which remains as stable as possible with variations in temperature, by virtue of high thermal inertia, low thermal conductivity and low expansion coefficient. It has not been practical to use lightweight base structures with low thermal inertias where thermal expansion of the material could lead to distortion and loss of accuracy.
SUMMARY OF THE INVENTION
According to the present invention there is provided for use in a coordinate measuring machine, a guideway support base which can remain substantially stable through fluctuations in ambient temperature, characterised in that the support base comprises a plurality of interconnected elongate tubular elements which provide a relatively lightweight structure having a through passage, heating means provided in the passage, and means for controlling the heating means, the heating means and the control means being capable of maintaining the temperature of the support base at a level at or above the ambient temperature.
Preferably the heating means comprises one or more electrically heated strips which can be suspended centrally in the passage.
Preferably also the elongate tubular elements are connected together in a rectangular configuration.
The elongate tubular elements may be formed of steel or a granite composition material, and external insulation may be provided.
Fan means may be provided within the elongate tubular elements to move air therethrough and thereby assist in providing an even distribution of temperature throughout the apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic perspective view of an apparatus according to the invention;
FIG. 2 is an enlarged section on 2222 of FIG. 1; and
FIG. 3 is a section on 3--3 of FIG. 2.
Referring to the drawing, a guideway base for use in a three axis co-ordinate measuring machine comprises a first pair of elongate tubular components 10 interconnected at their respective ends by a pair of tubular components 12 of reduced length whereby to define a rectangular configuration with a continuous passage therethrough. To reinforce the base an arrangement of elongate tubular struts 14 extend between inwardly facing external walls of the elements 10,12 in any suitable arrangement. The elements 10,12 and the struts 14 are formed of a material, preferably steel or a granite composite material comprising granite chippings and epoxy, which, in the tubular form, provides a lightweight base relative to a base formed of the material conventionally used, i.e. solid granite.
DETAILED DESCRIPTION OF THE INVENTION
To heat the base, a strip 16 incorporating one or more resistance wires is located within the elements 10,12 and the struts 14 to extend around the base. The strip 16 is preferably located centrally of the elements 10,12 by being suspended by arms 17 from side walls thereof, so as to avoid creating temperature gradients in the walls of the elements 10,12. The strip 16 is appropriately connected in an electrical circuit (not shown) for heating of the strip and thereby the base.
Additional heating strips may be used as necessary and in a modification the strip 16 may not extend around the whole base.
Within the base in the through passage there is provided a plurality of electrically operated fans 18. These effect circulation of the heated air throughout the base and thereby assist in providing a substantially uniform temperature throughout.
External insulation is provided for the elements 10,12 in order to avoid a temperature gradient across the walls. The insulation may be in a spaced relation with the external walls of the elements 10,12 to provide an air
REFERENCES:
patent: 326925 (1885-09-01), Sundin
patent: 2336506 (1943-12-01), Saunders
patent: 4250396 (1981-02-01), Moeller
Japanese Patent Abstract, vol. 8, No. 210 (M-238) (1647), Sep. 26, 1984.
Forest Products Journal, vol. 8, No. 7, Jul. 1958, A. O. Fiehl, "Reducing heat distortion in the knife and pressurebar assemblies of veneer lathes" pp. 216-218.
Haroian Harry N.
LK Limited
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