Measuring and testing – Inspecting
Patent
1988-06-17
1989-04-11
Myracle, Jerry W.
Measuring and testing
Inspecting
738665, G01M 1900
Patent
active
048194913
DESCRIPTION:
BRIEF SUMMARY
This invention relates to position-determining apparatus. Such apparatus may be arranged for performing a contour-following operation wherein the position of a machine member is determined in accordance with variations in the surface contour of an object. There exists a difficulty in that the inertia of a relatively heavy said machine member is inconsistent with rapid contour-following operations especially where sudden contour changes or contours of high gradients are involved. It is an object of the invention to reduce or overcome this difficulty.
A similar difficulty exists in position-determining apparatus arranged for performing a positioning operation wherein a machine member has to be moved and then halted in an accurately specified position. The inertia of the member may be inconsistent with rapid and accurate such positioning, and it is an object of the invention to reduce or overcome the inertia problem in the context of a positioning operation.
The invention is of use for contour-following or for positioning operations to be carried out in co-ordinate measuring machines where a probe having a sensing point is provided on a said machine member and where the inertia of the machine member is a difficulty in accurate sensing of the contour or in accurate positioning of the sensing point.
Examples of apparatus according to this invention will now be described with reference to the accompanying drawings wherein:
FIG. 1 is an elevation of a co-ordinate measuring machine being a primary positioning system.
FIG. 2 is an enlarged sectional detail of a probe shown in FIG. 1.
FIG. 3 is an enlarged section on the line III--III in FIG. 2.
FIG. 4 is an enlarged section on the line IV--IV in FIG. 2.
FIG. 5 is a diagram of a computer system for controlling the operation of the machine shown in FIG. 1 and probe shown in FIG. 2.
FIG. 6 is a control circuit diagram of a primary and a secondary positioning system used in the context of FIGS. 1 and 2.
FIG. 7 is a flow diagram of a program used in the above computer system.
FIG. 8 is an elevation of a tertiary positioning system.
FIG. 9 is an enlarged section on the line IX--IX in FIG. 8.
FIG. 10 is a control circuit diagram of the tertiary positioning system.
PRIMARY POSITIONING SYSTEM
Referring to FIGS. 1 to 6, the co-ordinate measuring machine (FIG. 1) comprises a table 36 supporting a column 33 for displacement relative thereto in the three directions X, Y and Z of the orthogonal co-ordinate system. The column 33 is supported on a carriage 34 for movement in the Z direction, the carriage 34 is supported on a track 35 for movement in the X-direction, and the track 35 is supported on the table 36 for movement in the Y-direction so that any combined movement in the three directions is possible. A motor 32Z is provided for moving the column 33 in the Z-direction. Corresponding motors 32X and 32Y are provided for moving the carriage 34 and the track 35 in the X and Y directions respectively. The position of the column 33 relative to the carriage 34 is measured by a position sensor 37Z being a scale and scale reader known per se and having an output 38Z. Corresponding sensors 37X, 37Y, having outputs 38X, 38Y, are provided for the X and Y-directions. The machine as described so far is also referred to herein as a primary positioning system 28.
SECONDARY POSITIONING SYSTEM AND SCANNING OPERATION
The column 33 has a free end to which is secured a probe 9 comprising a base or housing 10 (FIG. 2) having an axis 10A extending in the Z direction. Within the housing, there is provided a sensing member or tube 15 aligned with the axis 10A and connected to the housing by a pair of planar springs 13, 14 which allow limited axial displacement of the tube but constrain the tube against any other displacement. A laser light source 16 secured within the upper end of the tube projects a collimated beam of light through a beam splitter 17 onto a lens 18 secured within the lower end of the tube and adapted to focus the light to a spot 19 defining the sensing point of the probe 9.
REFERENCES:
patent: 3514869 (1970-06-01), Kelling
patent: 3741659 (1973-06-01), Jones, Jr.
patent: 4078314 (1978-03-01), McMurtry
patent: 4355904 (1982-10-01), Balasubramanian
patent: 4575942 (1986-03-01), Moriyama
Myracle Jerry W.
Renishaw plc
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