Patent ID: 7743478

Claim:
A method of changing knives in a device for mowing including a disc mounted to a rotating driver, the disc providing a mount for at least one knife having a circular aperture therein, defining a first opening having a mounting axis when a pivot pin is retained to said disc, such that the knife can rotate about said pivot pin between a first extended position and any retracted position, the disc constructed of a basic material thickness and comprising a mounting surface the disc also having a second opening therein; a knife adapter comprising a cylindrical aperture and a projection; said pivot pin comprising a first cylindrical section of a first diameter to fit into said cylindrical aperture in knife adapter, and a second cylindrical section, of a second diameter, with a groove defined by a groove width and a pin section thickness at the groove of a dimension less than said second diameter; a retainer constructed of a material thickness equal to or less than said basic material thickness of said disc, with a first key-hole shaped aperture defined by a first circular section adjacent a first end thereof with a first inside diameter larger than said second diameter of said pin and a slot shaped section with a width that is greater than said pin section thickness but less than said second diameter of said pivot pin adjacent a second end thereof; wherein said slot-shaped section of the retainer engages said groove of said pivot pin to retain said pivot pin while said projection of said knife adapter engages said retainer, said method comprising: (a) moving the knife adapter from below the disc so that the projection thereof is disposed into the second opening in the disc; (b) moving the pin so that it extends through the aperture in the knife and through said cylindrical aperture in the knife adapter and through the first opening in the disc; (c) moving the retainer so that the first circular section of the key-hole shaped aperture extends around the pin; and (d) moving the retainer toward the projection of the knife adapter until the first circular section of the key-hole shaped aperture of the retainer moves over the projection of the knife adapter and wherein the retainer engages the groove of the pin thereby securely holding the knife pivotally attached to the disc.