Circle dividing machine
An opto-mechanical device or machine tool that is used to produce precise pitch circles is referred to as a circle dividing machine or circle dividing machine . Such pitch circles are components of various measuring instruments and must therefore be precisely manufactured and easy to read .
Similar to length dividing machines , circular dividing machines have the task of providing the most important component of a measuring instrument with an exact line division ( measuring marks ). For this purpose, the circle (or rod) is periodically moved by a fixed step size, whereupon a fixed shredding mechanism or a photomechanical apparatus makes a line of a certain length.
Required precision of the pitch circles
A particularly high level of accuracy is required for astronomical and geodetic instruments, for example telescopes in observatories, universal instruments or theodolites . These devices have two mutually perpendicular partial circles of glass or noble metal, the angular position by special microscopes is read with a precision of at least 1 "(0.0003 °). This angle measurement depends essentially on the precision of the divisions on the graduated circles from. In precision theodolite have the glass circles have radii of about 40 mm. Each individual graduation line must therefore be applied to the partial circle with an accuracy of 0.0001 mm.
Working principle
The circle dividing machines developed in the 20th century have a particularly precisely divided, vibration-free base circle ( mother circle ) with a diameter of up to 1 meter. The metal or glass circles to be divided are mounted centrally on it and the graduation lines are scored radially in defined increments or produced photomechanically. In the past, circular rotation was carried out by means of an endless fine movement (worm wheel ) and a reading microscope and was automated in the 1960s using optical-electronic measuring methods.
After the circle division, the circle numbering machine has to come into action, but its operations can be integrated today. In the case of an opto-mechanical or electronic second theodolite with up to 20,000 graduation marks, the line width is 0.006 mm and the lettering height is 0.1 mm.
History
Good pitch circles already existed in the late Middle Ages for the still free-eyed measuring instruments such as quadrants , sextants and meridian circles , but they were only made by machine (and therefore more precisely) from the 18th century. The graduation was transferred to the graduated circle to be produced by a round graduated disk that could be rotated around a vertical axis. The base graduated disk was divided into degrees and fractions (5 or 10 arc minutes ) at the edge , and above it sat the radially displaceable tearing mechanism . The metal circle to be divided was clamped centrally on the axis of the graduated disk directly under the teardrop and rotated with the graduated disk from one division to the next. This adjustment was initially done manually, later with magnifying glasses . Around 1770, Jesse Ramsden (1735–1800) developed a mechanical method with an endless screw that meshed with a helical gear on the graduated disk and ensured the exact increment in each case.
From around 1800, the setting was refined using reading microscopes , as they were most precisely manufactured by the Reichenbach optical-precision engineering workshop for the theodolites. Its dividing machine from 1802 contributed significantly to Bavaria's status in geodesy and instrument making.
Web links
- Circle dividing machines from Kern Aarau from around 1820 to 1965
- Meyers 1905: Length and circle dividing machines
- Dividing machine with mother circle
Individual evidence
- ^ E-Lexicon: Part machine
- ↑ for circles of subordinate accuracy also by snapping into marginal recesses of the mother circle
- ↑ Georg von Reichenbach's circle dividing machine 1802, Bavarian Academy of Sciences. ( Memento of the original from December 4, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
