Mobility aid

1. A mobility aid assembly for lifting and lowering a user comprising an articulated lifting arm releasably mounted to a base structure, wherein:

a first portion of the lifting arm is operable between a lowered position and a raised position by a linear actuator;

a first end of the linear actuator is configured to remain attached and pivotally connected to the first portion of the lifting arm; and,

a second end of the linear actuator is provided with a mounting boss, the mounting boss is provided with a first connecting element for releasable connection to a complementary second connecting element provided on a second, fixed upright portion of the lifting arm, the first connecting element comprises a transverse U-shaped slot having parallel sides and the complementary second connecting element comprises a transverse pin, wherein the second end of the linear actuator is positioned to slidingly engage the transverse U-shaped slot with the transverse pin to slidingly releasably mount the second end of the linear actuator on the complementary second connecting element so as to avoid injury to the user if the linear actuator moves the first portion of the lifting arm to an excessively lowered position in which the first portion of the lifting arm impinges on the user, and wherein the second end of the linear actuator disengages from the complementary second connecting element when an upward force acting on the first portion of the lifting arm exceeds the combined weight of the first portion of the lifting arm and that of the linear actuator.

2. The assembly of claim 1 wherein the base structure comprises:

a hollow body having outer ends; and

a drive wheel provided at each outer end, each drive wheel being driven by respective electric motor modules located within the hollow body.

3. The assembly of claim 2 wherein each electric motor is controllable for synchronized rotation of the wheels for forward and rearward movement of the assembly and for contra-rotation of the wheels for rotation of the assembly about a vertical axis.

4. The assembly of claim 1 further comprising a forwardly directed fork, the fork comprising two fork elements extending from the base structure, wherein:

each fork element includes an outer end;

each outer end is provided with a swiveling castor; and

each castor is provided with a locking mechanism for locking the direction of movement of the castor at a desired angle relative to a horizontal centerline of the assembly.

5. The assembly of claim 4 wherein:

each fork element is releasably mounted to the base structure;

each fork element is arranged for rotation about a respective vertical axis at the base structure;

each fork element is rotatable between a first direction parallel to the horizontal centerline of the assembly and a second splayed direction; and

a separation between the outer ends fork elements is greater than a separation of the vertical axes at the base structure.

6. The assembly of claim 5 wherein:

the fork elements move from the first direction parallel to the horizontal centerline to the splayed direction if the castor at each outer end fork element is locked at an outwardly splayed angle relative to a centerline of the respective fork element and the assembly is driven in a forward direction; and

the fork elements return to the first direction when the assembly is driven in a rearward direction with the castors locked in the outwardly splayed angle.

7. A method of avoiding injury to a user of a disability aid assembly if a first articulated portion of a lifting arm of the assembly is lowered by a linear actuator of the assembly to a point at which the first articulated portion is driven into contact with the user by retraction of the linear actuator, the method comprising the steps of:

slidably engaging a transverse U-shaped slot located on a lower end of the linear actuator with a transverse pin located on a second, fixed upright portion of the lifting arm; wherein an outer end of the linear actuator is configured to remain attached and pivotally connected to the first articulated portion of the lifting arm; and

disengaging the lower end of the linear actuator from the second, fixed portion of the lifting arm when a force cannot exceed a combined weight of the articulated portion of the lifting arm and the linear actuator.

8. A mobility aid assembly for lifting and lowering a user comprising an articulated lifting arm releasably mounted to a base structure, wherein:

a first portion of the lifting arm is operable between a lowered position and a raised position by a linear actuator;

a first end of the linear actuator is configured to remain attached and pivotally connected to the first portion of the lifting arm; and,

a second end of the linear actuator is provided with a mounting boss, the mounting boss is provided with a first connecting element for releasable connection to a complementary second connecting element provided on a second, fixed upright portion of the lifting arm, the first connecting element comprises a transverse U-shaped slot having parallel sides and the complementary second connecting element comprises a transverse pin, wherein the second end of the linear actuator is positioned to slidingly engage the transverse U-shaped slot with the transverse pin to slidingly releasably mount the second end of the linear actuator on the complementary second connecting element so as to avoid injury to the user if the linear actuator moves the first portion of the lifting arm to an excessively lowered position in which the first portion of the lifting arm impinges on the user.