Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1987-04-30
1989-09-05
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356152, G01N 2186
Patent
active
048641480
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for detecting and monitoring shaft position and changes in position of rotating shafts.
In known apparatus of this type, U.S. Pat. No. 4,698,491, a ray source with an associated ray receiver is mounted on one shaft while another shaft with which it is to be aligned supports a prism. The ray source continuously directs a light ray towards the prism which continuously reflects the light ray back to the ray receiver. A special clocking device is associated with the rotating shafts permitting output signals supplied by the ray receiver to be related to the position of the light ray. In addition to the clocking device it is necessary to have transmitting means such as slip rings with slip ring brushes, transmitters and the like consisting of a rotor and a stator for the transmission of the output signals supplied by the ray receiver, from the one rotating shaft to the processing device.
In order to improve upon the above-mentioned involved and unreliable transmitting means the German unexamined specification No. 3,419,059 describes an arrangement with a number of ray sources, ray receivers and prisms aimed at each other in different positions on the base or housing of two machines, whose shafts are to be monitored so that it is only the changes in the relative position of the two machines which are detected and monitored. This known device only detects such changes in the relative position of the shafts as are a cause of changes in the relative position of the machines. However it is also possible for machines which are coupled together to undergo a change in the relative shaft positions, for example owing to bearing wear, without this involving a change in the relative position of the machine. Such changes, which also lead to critical operational conditions, are not detected by the last-mentioned known device.
An object of the invention is to devise an apparatus for direct monitoring of shaft position in such a way that the previously employed involved and unreliable means for transmission of position signals from the receiver side and position signals from one rotating shaft to the processing means may be dispensed with.
In the apparatus in accordance with the invention it is not necessary for any electrical position signals to be transmitted from one rotating shaft to a stationary processing device, because it is only the prisms, at least one of which is mounted on each shaft, that rotate with the shafts and by way of respective light rays cooperate with the respective ray receivers included in the receiver system. The position of each shaft is monitored in a manner incorporated in the reference system and the electrical position signals produced may be compared with stored output signals and employed for monitoring the shaft position and detecting departures in position from initial positions.
The apparatus in accordance with the invention is suitable both for monitoring individual shafts in a reference system and also for monitoring the proper alignment of two coaxial shafts, and more especially elastically coupled shafts connecting two machines mounted with a clearance therebetween.
The invention will now be described in detail with reference to the drawing which shows embodiments thereof.
FIG. 1 shows one of the rectangular prisms used in the apparatus of the invention as seen from the side and in different angular settings in relation to the incident light.
FIG. 2 shows the prism from above in two different angular settings with reference to the incident light ray.
FIG. 3 shows a lateral view of the laser diode employed in the apparatus of the invention as a ray source.
FIG. 4 shows the laser diode of FIG. 3 end-on and looking towards the ray outlet.
FIG. 5 shows an analogous photoelectric semi-conductor position detector, used in the apparatus of the invention as a ray receiver, in section to indicate the principle of operation.
FIG. 6 shows the position detector of FIG. 5 from the front and in a dual axis version.
FIG. 7 is a cross section taken through the detector
REFERENCES:
patent: 2703505 (1955-03-01), Senn
patent: 3603691 (1971-09-01), Hamilton
patent: 4518855 (1985-05-01), Malak
patent: 4627725 (1986-12-01), Nishio et al.
patent: 4698491 (1987-10-01), Lysen
Busch Dieter
Lysen Heinrich
Wagner Karl
Fiddler Robert W.
Nelms David C.
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