Method and apparatus for sensing pressure

• US 4,275,393 A
• Filed: 07/03/1979
• Issued: 06/23/1981
• Est. Priority Date: 07/03/1979
• Status: Expired due to Term

• Current Assignee: Polyvend, Inc. (Crane Company)
• Original Assignee: Polyvend, Inc. (Crane Company)
• Inventors: Johnston, Max M.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US06/054,420
• Time in Patent Office: 721 Days
• Field of Search: 340/688, 340/626, 73/431, 73/705, 73/709, 250/231 R, 250/231 P, 250/231 SE, 324/96, 324/157
• US Class Current: 340/688
• CPC Class Codes: G01D 13/26 adapted to perform a further operation, e.g. making electrical contact
• CPC Class Codes: G01D 5/34 the beams of light being detected by photocells
• CPC Class Codes: G01L 19/12 Alarms or signals

Abstract

A pressure sensing device has a light source, and an optical sensor for externally sensing a predetermined change in the pressure within a sealed system which has a conventional gauge. Illumination from the light source is reflected off of the gauge dial and detected by the optical sensor. When the pressure in the sealed system changes a predetermined amount, the needle on the gauge moves so as to interrupt the illumination reaching the optical sensor. The optical sensor in turn produces a voltage that can be used to turn on a light or other indicator.

Claims

1. In a sensing apparatus for sensing the position of an indicator needle in a pressure gauge having an unaltered dial located behind the indicator needle, the sensing apparatus has a supporting clamp removably attachable to the gauge by a set-screw, the clamp supports a means for illumination and a light sensing means, an improvement wherein:

said clamp is formed with a planar first side with a hole therein such that the gauge is receivable within said hole, a planar base is connected at a first edge to an edge of said planar first side and is essentially perpendicular thereto, a planar second side is connected to a second edge of said base essentially parallel to said first side, said second side is positionable immediately in front of a glass cover over the indicator needle and dial of the gauge when the gauge is received within said hole in said first side, an elongated hole in said second side;

said means for illumination and said light sensing means are mounted within a shaped rigid housing and spaced with respect to one another, said housing has first and second surfaces on opposite sides thereof oriented at an angle with respect to one another;

a first region of said housing is extendable through said elongated hole in said second planar member, said first and second surfaces engage opposite edges of said elongated hole to position said housing along with said means for illumination and said light sensing means with respect to said clamp and to limit movement of said first region of said housing toward the gauge;

removable locking means to retain said housing within said elongated hole in said second planar member;

means for supplying energy connected to said means for illumination in said housing by removable connection means;

means for comparison connected to said light sensing means in said housing by said removable connection means to continuously monitor only a single indicia generated by said light sensing means, said single indicia is proportional to an amount of light generated by said means for illumination reflected off of a selected region of the unaltered dial and sensed by said light sensing means, said means for comparison compares said sensed single indicia to a preselected value, when said sensed single indicia drops below said preselected value due to the indicator needle moving between said means for illumination and the selected region of the dial, said means for comparison generates a predetermined signal;

means for latching responsive to said predetermined signal to continuously energize a means for visually signaling a selected pressure condition until said means for visually signaling is manually reset.

2. The improved sensing apparatus according to claim 1 wherein:

said means for comparison includes a Darlington connected pair of transistors, responsive to said sensed single indicia and said means for latching includes a semiconductor element having a stable conducting state and a stable non-conducting state such that when said means for comparison generates said predetermined signal said semiconductor element switches from said stable non-conducting state to said stable conducting state to continuously energize said means for visually signaling until said means for latching is manually reset.