Security wheel apparatus for deterring theft of manually operated wheeled vehicles

A security wheel unit for attachment to a shopping cart to inhibit the unauthorized use and removal of the cart from a designated use area, comprising:

• wheel means having a closed chamber formed therein;
• axle means journalled to said wheel means, said axle means being attached to a cart and fixed against rotation about its longitudinal axis;
• rotation-inhibiting means disposed within said chamber and including a locking member movable between an unlocked position and a locked position in which it engages said axle means to prevent rotation of said wheel means;
• counting means disposed within said chamber;
• sensor means disposed within said chamber for sensing rotation of said wheel means and for generating an output signal which can be counted by said counting means, said sensor means including a mercury switch positioned to open and close at least one time for each revolution of said wheel means;
• and
• actuating means disposed within said chamber and operative in response to said counting means, to cause said rotation-inhibiting means to be moved into said locked position after a predetermined count has been reached.