[54] PHOTOELECTRIC PROXIMITY SENSOR HAVING SHUTTER ADJUSTMENT MEANS FOR SENSING REGION DISTANCE
[75] Inventor: Eugene F. Duncan, Wauwatosa, Wis.
[73] Assignee: Eaton Corporation, Cleveland, Ohio
[21] Appl. No.: 627,520
[22] Filed: Dec. 14,1990
[51] Int. CI.' G01V 9/04
[52] U.S. CI 250/221; 250/222.1;
340/556
[58] Field of Search 250/221, 222.1, 237 R;
340/555, 556, 557
[56] References Cited
U.S. PATENT DOCUMENTS
178,391 6/1976 Wale .
3,447,862 6/1969 Elpern 350/269
3,715,149 2/1973 Freeland 350/58
3,843,267 10/1974 Vital et al 356/225
4,282,430 8/1981 Hatten et al 250/221
4,306,147 12/1981 Fukuyama et al 250/221
4,778,254 10/1988 Gilliland, III et al 350/269
Primary Examiner—David C. Nelms
Assistant Examiner—S. Allen
Attorney, Agent, or Firm—L. G. Vande Zande
[57] ABSTRACT
A shutter is manually rotated across a circular aperture and into a light beam projecting through said aperture to selectively block a predetermined proportion of the light beam, thereby reducing intensity of light emitted to shorten the target sensing region distance for a photoelectric proximity sensor. First and second edges of the shutter intersect at a corner common to both edges and greater than ninety degrees. The shutter pivot is located so the corner traverses the aperture and thus the light beam substantially diametrically to cause the first edge to progressively reduce the light beam, the second edge sequentially progressively reducing the remaining half-circle of light beam upon continued rotation of the shutter.
6 Claims, 3 Drawing Sheets
