Patents by Inventor Chang Wan-Li

Chang Wan-Li 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: 5022118
    Abstract: A ladder joint with an engagement spring member on it for locking/unlocking the ladder joint into position. The ladder joint has a fixed member and a movable member. The movable member has a circular portion with fixing slots on its outer circumference. The fixed member has an annular track which slidably receives the circular portion of the movable member. Both the fixed and the movable members have a straight portion for connecting with the ladder pieces. The engagement spring member is a rounded flat spring which has an extended edge on one of its ends which normally spring loads the rectangular slug into one of the fixing slots as set by the user.
    Type: Grant
    Filed: June 25, 1990
    Date of Patent: June 11, 1991
    Assignee: Wan Dean Industry Co.
    Inventor: Chang Wan-Li