Geometrical instruments – Miscellaneous – Light direction
Patent
1989-08-03
1991-08-20
Cuchlinski, Jr., William A.
Geometrical instruments
Miscellaneous
Light direction
25023114, 33424, 33 1PT, G01B 356, G01B 524, G01B 730
Patent
active
050402986
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a protractor in accordance with the preamble of claim 1.
Mechanical protractors or angular measuring systems with two arms pivoting relative to one another about a central shaft and with an angular reading in the form of a vernier scale for the purpose of determining the angle set between the two arms have been known in the art for a long time. They generally possess, at least in the case of precision instruments, a vernier angle scale with the aid of which the angle formed between the two arms can be read off to an accuracy of within one tenth of a degree or to one minute precisely. Since reading off such scales with their multiplicity of relatively closely adjacent graduations is not universally popular, wrong measurements or misreadings are a frequent occurrence.
The objective of the present invention, therefore, is to propose a protractor which, on the one hand, excludes the danger of misreadings, and digitally displays the angle set between the two arms, and which, on the other hand, makes use of currently available electronic means of resetting and reading transformation.
This is achieved in the invention by means of an protractor as described hereinafter.
With the aid of the enclosed drawing, an advantageous embodiment of an protractor in accordance with the invention is described below, and the design problems which had to be solved are explained.
The drawings are as follows:
FIG. 1 shows a plan of such a protractor in which the fixed arm is represented by broken lines in the eight 45.degree. segments of a circle relative to the rotating arm,
FIG. 2 shows a cross-section through an electromechanical measuring device which should be located such that it can rotate about the rotational axis of the protractor and should be protected against mechanical influences,
FIGS. 3a, 3b and 3c show the three main components of the measuring device according to FIG. 2, each in a plan view,
FIG. 4a shows a partial section through the protractor with a first embodiment of a central mounting arrangement,
FIG. 4b shows a partial section through the protractor with a second embodiment of a central mounting arrangement,
FIG. 5 shows a plan view of a central clamping element in the protractor, which is intended to ensure that the unit is locked and unable to rotate, without affecting the electromechanical measuring device,
FIG. 6 shows the clamping element as in FIG. 5 in cross-section, and
FIG. 7 shows a protractor in accordance with the invention for a special application.
In FIG. 1 it can be seen that the protractor in accordance with the invention largely corresponds to a conventional mechanical universal bevel protractor as far as its primary mechanical components are concerned, i.e. a fixed arm 1 which is either firmly attached or firmly attachable to the base 11 (FIG. 4) of the protractor, a movable arm 3 which is capable of rotating, as far as possible without play, about a rotational axis A, which arm is firmly attached to the cover 2 of the protractor, and a central locking nut 4. It is also advantageous for it to have, as shown here, a device operated by a control knob 5 and described in further detail below for setting small angular changes precisely. It is further recommended that the protractor in accordance with the invention be provided with the necessary means to permit precise setting of the calibration mark where the movable arm 3 is exactly flush with the fixed arm 1. The means required to this end and the possible means for attaching the movable arm 3 to the rotating part 17 are not, however, integral to the present invention and are therefore not described further.
FIG. 2 illustrates the approximate construction of a capacitive measuring device as advantageously used in the protractor according to the invention. In addition to an electronic system, which is not further described here, it consists, in the case of a 3-disc model, essentially of a disc-shaped first electrode disc 6 with patterned electrode areas (FIG. 3a), an electrostatic shield 8 with apertures 9 and
REFERENCES:
patent: 4358898 (1982-11-01), Johnson
patent: 4442606 (1984-04-01), Graham et al.
patent: 4492031 (1985-01-01), Koenuma
patent: 4513512 (1985-04-01), Fischer
Cuchlinski Jr. William A.
Dowling William C.
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