US Patent 10064464 Shoe with retractable spike mechanism for canes and crutches

A shoe for canes and crutches composing a cylindrical tubular member having an end mounted to the end of a shaft or crutch, and the other end having a central bore axially extending inwardly a defining a first bottom and coaxially disposed second bore having a smaller diameter than said first bore and extending a second predetermined distance defining a second bottom. A circular plate with a central through opening biased by a coil spring member coaxially disposed around a post. A cap member is sandwiched between a knob connected to the plate for rotating the latter and causing it to move along the post to engage the irregular through opening to a cutout in the post.