Geometrical instruments – Gauge – Coordinate movable probe or machine
Reexamination Certificate
2000-12-01
2002-08-27
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Coordinate movable probe or machine
C033S0010MP
Reexamination Certificate
active
06438857
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a coordinate measurement device with a base frame, a measurement table supported at the latter for holding an object to be measured, a sensing device for sensing the surface of the object to be measured, and with a positioning device for moving the sensing device in three spatial axes over the measurement table, which positioning device is mounted at the base frame and carries the sensing device.
b) Description of the Related Art
Coordinate measurement devices of the type mentioned above are used for sensing the shape of an object to be measured and for accurately measuring this object. Apart from first-time determination of the geometric data of such an object, coordinate measurement devices can also be used to check the dimensional stability of objects in a manufacturing line.
Coordinate measurement devices are high-precision instruments whose measuring accuracy exceeds that of the manufacturing equipment utilized for producing the object to be measured. In contrast to manufacturing devices, however, the forces occurring during a sensing process remain small.
For sensing larger objects, the prior art discloses coordinate measurement devices in portal-type construction in which the sensing device is arranged at a vertically displaceable spindle sleeve which is mounted at a crosspiece arranged between the two portal columns so as to be displaceable along this crosspiece. Together, the columns with the crosspiece form a portal which spans a measurement table and is movable along the same in air bearings. Due to the portal straddling the measurement table, this known construction provides good structural rigidity, but is relatively uneconomical and needs considerable space. In addition, free access to the measurement table is restricted by the portal-type construction and, with heavy workpieces, the orientation of the precision guides is influenced by the occurring introduction of forces, which results in inaccurate measurements.
In order to meet the requirements for high measuring accuracy, high-precision bearings, usually in the form of air bearings, have been used heretofore in coordinate metrology. A high degree of purity of the surrounding atmosphere and a temperature level that is as constant is possible are required for air bearings, so that these coordinate measurement devices must be operated in special rooms and can not be set up in the immediate vicinity of manufacturing equipment.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to provide a coordinate measurement device which is capable of working with high accuracy and in a highly dynamic manner and which also permits use in the immediate vicinity of manufacturing.
This object is met by a coordinate measurement device of the type mentioned above in which the positioning device has a first slide which is guided at the base frame in a first direction and which is movable on one side of the measurement table toward and away from the latter and on which a second slide is movable in a second direction vertical to the first direction, this second slide being provided at its end area remote of the measurement table—considered in its movement direction—with a supporting portion which projects lateral to the measurement table and at which there is arranged a U-arm or stirrup arm which projects over the measurement table in a direction vertical to a principal work plane of the measurement table and which carries the sensing device at its free end over the measurement table and is constructed as an element that is rigid per se, wherein the first slide and the front area of the second slide situated in front of the supporting portion considered in the movement direction of the first slide can be moved in under the measurement table during the movement of the positioning device toward the measurement table.
Owing to the rigid construction of the stirrup arm and the consequent absence of any guides at the latter, it is possible to construct the stirrup arm in virtually any desired manner without restriction and—in contrast to a surrounding portal at which the sensing device is arranged so as to be movable—there is also no troublesome location-dependent bending of the stirrup arm (depending on its position relative to the measurement table). In cooperation with the supporting portion arranged laterally next to the measurement table, a superior accessibility to the entire surface of the measurement table over which the sensing device can be guided is achieved with the coordinate measurement device according to the invention.
Due to the fact that the stirrup arm used in the arrangement according to the invention has a substantially smaller mass than a portal extending around the measurement table, the coordinate measurement device according to the invention also works with appreciably increased dynamics of the entire system compared to the latter with respect to both principal and secondary processes. In addition, there is a wide variety of possible installation positions of the sensor (vertical, horizontal or other defined position). Moreover, relatively large bearing bases can be provided for the moving parts, which likewise benefits the measuring accuracy and structural rigidity of the device according to the invention.
A particularly compact construction results in that part of the positioning device can be moved under the measurement table. This allows the positioning device to be constructed with a wide, stable base and, accordingly, high rigidity, which again results in high measuring accuracy. When completely moved in, the supporting portion preferably comes into contact with a side edge of the measurement table. Since the supporting action relative to the base frame is caused for the most part by elements which are movable under the table, the supporting area on the side of the supporting portion remote of the measurement table can be relatively narrow and, therefore, particularly the area of the base frame next to the measurement table can also be kept compact with respect to dimensions so that the total setup surface needed for the coordinate measurement device is kept small.
Because of the relatively small mass of the positioning device (compared to a portal construction), the required acceleration forces and retardation forces for feeding the sensing device are also small. This results in a high positioning speed and therefore in heightened dynamics of the coordinate measurement device according to the invention.
Further, the very extensive freedom with regard to the shaping of the stirrup arm makes it possible to optimize the latter with respect to geometry and selection of material while taking into account the forces and moments occurring in a sensing process.
A particularly compact construction for the positioning device is preferably provided in that the stirrup arm is guided at the side of the supporting portion of the second slide facing away from the measurement table. In addition, the guide rails for the movement of the two slides relative to the measurement table can also be kept relatively short in this way, since the installation space needed for the guides of the stirrup arm does not occur as an idle path at these guide rails.
In an advantageous construction of the coordinate measurement device, the bearing support of the stirrup arm at the supporting portion is located approximately at the height of the sensing device provided at the free end of the stirrup arm. Accordingly, tilting moments occurring at the guides of the stirrup arm during a sensing process can be kept small so that measuring accuracy is improved.
The second slide preferably forms a substantially L-shaped section which is formed by the supporting portion extending substantially vertical to a principal work plane of the measurement table and is provided with guide devices for displaceable bearing support of the stirrup arm and by the front portion of the second slide, which front portion is connected with the supporting portion
Jacobs Klaus
Piwek Volker
Walther Joerg
Carl-Zeiss Stiftung
Gutierrez Diego
Hayleck Ryan T.
Rees Smith LLP
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