Articulated device for the probe head of a coordinate measuring apparatus

#The invention relates to an articulated device for the probe head of a coordinate measuring apparatus. The articulated device includes at least two rotational joints for angularly aligning the probe head.

#Articulated devices have been known for some time. There is the so-called continuously rotatable articulated device wherein the rotational angle can be continuously adjusted via a corresponding motor and the exact rotational angle is supplied via an encoder. Also known are the latching articulated devices wherein only a limited number of rotational angles can be adjusted. In a known latching articulated device of Carl Zeiss having the product designation “RDS”, two interacting crown gears of a so-called Hirth meshing are used which, in the latched state, engage in one another and thereby latch the particular adjusted rotational angle.

#A continuously rotatable articulated device is disclosed in U.S. Pat. No. 4,888,877. Here, an articulated device is shown which has two motor-driven rotational joints which are continuously pivotable and the rotational axes of which are perpendicular to each other. With reference to the different rotational angles, corrective values are stored so that the probe pin need not be newly calibrated for each change of the rotational angle of the rotational joints. The corrective values define the position of the rotational axes to each other. Furthermore, alternatively or in addition, corrective values can be provided with respect to angular position deviations and the running deviations of the rotational axes. However, with respect to the realization of these last-mentioned corrections, it is not precisely described how these corrections can be advantageously utilized.

#The invention will now be described with reference to the drawings wherein:

#FIG. 1 is a perspective view of an articulating device for a probe head of a coordinate measuring apparatus;

#FIG. 2 is a schematic of the articulating device of FIG. 1;

#FIG. 1 shows an articulating device which is here configured as a so-called latching articulating device. The articulating device is attached to a horizontally aligned measuring arm 8 of a stand-type measuring apparatus and has two rotational joints (14, 15) which connect the components 1 and 2 as well as the components 2 and 3 rotatably with each other. The rotational joints (15, 14) define the rotational axes aA and aB. The articulating device includes so-called Hirth gears (6, 7) for tightly latching the adjusted rotational angles. These gearings are pairs of interacting bevel gears which mesh with each other. A pneumatic cylinder is disposed in the interior of the articulating device in order to change the rotational angles of the rotational joints (14, 15). The component 2 can be lifted relative to the component 1 as well as the component 3 relative to the component 2 via the pneumatic cylinder. An electric motor is provided for each of the rotational joints via which the rotational angle of the particular rotational joint (14, 15) can be adjusted. After the desired rotational angle is reached, the lifted components 1 and 2 or 2 and 3 are again pulled together by the pneumatic device.

#In FIG. 1, a probe head 4 of the switching type is mounted in the receptacle of the articulating device. A probe pin 11 is, in turn, held on the probe head 4. The probe pin 11 with a probe ball 12 is held so that it can be exchanged. An electrical signal is triggered by the probe head 4 when the probe ball 12 comes into contact with a workpiece. It is understood that an optical probe head or a measuring probe head can also be used. The probe head 4 is attached to the holder plate 3 by means of an adapter 5.

#The measurement values are recorded by the coordinate measuring apparatus during a measurement and are corrected in the correction unit 22 in accordance with a mathematical model. The correction unit 22 is shown here only schematically and is usually the computer of the coordinate measuring apparatus. A microprocessor of the correction unit itself can be alternatively used and can be arranged, for example, in the control of the coordinate measuring apparatus or even in the articulating device itself.