| 主权项 |
1. A drive unit for a cart having a lower frame mounted on swivel wheels and a longitudinal axis and a transverse axis, said drive unit having
a fixed top plate for attachment to the lower frame of the cart, said fixed top plate having a first pivot hole for a pivot pin; a pivot plate having a second pivot hole for the pivot pin and suspended from the fixed top plate by the pivot pin, said pivot plate further having a downwardly extending attachment plate with a hole; a drive wheel carriage having a yoke carried by the pivot plate and in which a reversible motor and at least one drive wheel are mounted, said yoke mounted on an arm with a downwardly extending flange with an outwardly extending pin, said pin passing through the hole in the attachment plate for rockably and rotatably suspending the yoke on the pivot plate by the pin, said yoke resiliently biased against the pivot plate by a spring such that the at least one drive wheel is out of contact with the supporting surface and selectively biased by an inflatable air bag for forcing the drive wheel into contact with the supporting surface against the resisting force of the spring, whereby the drive unit may propel a cart forward and reverse when the at least one drive wheel is aligned with the cart's longitudinal axis and forced into contact with supporting surface by the air bag and from side-to-side when the at least one drive wheel is aligned with the cart's transverse axis and forced into contact with the supporting surface. |
