Patents by Inventor Shaun D. Johnson

Shaun D. Johnson has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 7699053
    Abstract: Disclosed is an apparatus and method for operating powered air-purifying respirators safely in explosive atmospheres. The apparatus and method utilize a current control means for sensing a current flow from a battery to a motor, and stopping the current flow when the current flow exceeds a threshold value for a predetermined amount of time. Upon sensing that the current flow has exceeded the threshold value for the predetermined amount of time, the current control means immediately stops the current flow. The apparatus and method provides sufficient power to properly start and operate the motor by providing a soft start to the motor by limiting the duration of higher than threshold operating current to intervals shorter than the predetermined amount of time. Pulse width modulation is used to ramp-up the motor to speed by supplying pulses of energy to the motor that will not cause the current control means to stop the current flow.
    Type: Grant
    Filed: December 16, 2005
    Date of Patent: April 20, 2010
    Assignee: E.D. Bullard Company
    Inventors: Douglas V. Johnson, Shaun D. Johnson