Ignitability test method and apparatus

• US 5,052,817 A
• Filed: 10/04/1990
• Issued: 10/01/1991
• Est. Priority Date: 11/30/1989
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Bailey, James W., Bement, Laurence J., Schimmel, Morry L.
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US07/593,412
• Time in Patent Office: 362 Days
• Field of Search: 374/8, 73/167, 102/204, 102/470, 102/202.5, 102/200
• US Class Current: 374/8
• CPC Class Codes: G01N 25/50 by investigating flash-point; by investigating explosibility

Abstract

An apparatus for testing ignitability of an initiator includes a body having a central cavity, initiator holder for holding the initiator over the central cavity of the body, an ignition material holder disposed in the central cavity of the body and having a cavity facing the initiator holder which receives a measured quantity of ignition material to be ignited by the initiator and a chamber in communication with the cavity of the ignition material and the central cavity of the body, and a measuring system for analyzing pressure characteristics generated by ignition of the ignition material by the initiator. The measuring system includes at least one transducer coupled to an oscillograph for recording pressure traces generated by ignition.

Claims

1. An apparatus for testing ignitability of an initiator, comprising:

a body having a central cavity, an upper cavity and a lower cavity, the upper and lower cavities being disposed at opposite ends of the central cavity and collectively forming with the central cavity a central passageway passing through the body;

an initiator holder for holding the initiator over the central cavity of the body;

an ignition material holder disposed in the central cavity of the body and having a cavity facing the initiator holder which receives a measured quantity of ignition material to be ignited by the initiator and a chamber in communication with the cavity of the ignition material holder and the central cavity of the body;

an adaptor removably mounted in the upper cavity and abutting the upper end of the initiator holder;

a firing mechanism slidably received in a bore extending through the adaptor and being movable into contact with the initiator, thereby firing the initiator;

a drop weight means to provide actuation of the firing mechanism;

a guiding means to guide the drop weight means to concentrically impact of the firing mechanism;

an accelerator means mounted above the drop weight means to record time of impact of the firing mechanism by the drop weight means; and

means, in communication with the central cavity of the body, for measuring pressure characteristics generated by ignition of the ignition material by the initiator.

2. An apparatus for testing ignitability as claimed in claim 1, wherein the measuring means comprises at least one transducer mountable in the body to be in communication with the central cavity and outputting a signal indicative of pressure generated upon firing of the initiator into the ignition material, and an instrument for measuring and recording the pressure as a function of time.

3. An apparatus for testing ignitability as claimed in claim 2, wherein the analyzing means further comprises means for determining pressure at one millisecond after firing the initiator and peak pressure, the ratio of one millisecond pressure to peak pressure defining a value of ignitability.

4. An apparatus for testing ignitability as claimed in claim 2, wherein the at least one transducer is a piezoelectric transducer.

5. An apparatus for testing ignitability as claimed in claim 2, wherein the analyzing means comprises a magnetic tape recorder and oscillograph coupled to and recording the output of a transducer which is mountable in the body to sense ignition-induced pressure.

6. An apparatus for testing ignitability as claimed in claim 2, wherein the at least one transducer is mounted orthogonally to a longitudinal axis of the ignition material holder at a position spaced above the radially oriented holes of the ignition material chamber.

7. An apparatus for testing ignitability as claimed in claim 1, wherein the ignition material cavity is hemispherically shaped.

8. An apparatus for testing ignitability as claimed in claim 2, wherein the analyzing means further comprises means for determining output delay by recording the time interval between impact of the firing mechanism as indicated by the accelerometer means and pressure in the central cavity reaching 100 psi.

9. A method for testing ignitability of an initiator comprising determining an output delay and a function time of an initiator and determining a ratio of a one millisecond pressure value to the peak pressure, the ratio of said pressure values defining a value of ignitability, and comparing the ratio to ratios corresponding to other combinations of initators and ignition materials similarly tested to determine relative differences in ignitability.