Quick attach rotary mower blade system

1. A quick attach rotary mower blade system, comprising:

a spindle extending through a flange mounted on a mower deck, the spindle having a first pair of fan-shaped projections extending radially outwardly from a lower end thereof;

a spring-loaded collar having a bore through which the lower end of the spindle extends and having a second pair of fan-shaped projections extending radially outwardly from the bore; and

a mower blade having a mounting hole including a circular center opening and a pair of fan-shaped openings extending radially outwardly therefrom; the mower blade installable on the spindle by aligning the pair of fan-shaped openings with the first and second pairs of fan-shaped projections, moving the mower blade and spring-loaded collar upwardly, and rotating the mower blade and spring-loaded collar 90 degrees to interlock the second pair of fan-shaped projections between the first pair of fan-shaped projections.

2. The quick attach rotary mower blade system of claim 1 wherein the spring-loaded collar includes a conical compression spring positioned in an upwardly opening cavity.

3. The quick attach rotary mower blade system of claim 1 further comprising a spacer positioned between the spring-loaded collar and the flange.

4. The quick attach rotary mower blade system of claim 1 further comprising a circumferential shoulder around the outer circumference of the spring loaded collar.

5. A quick attach rotary mower blade system, comprising:

a spindle extending vertically through a spring-loaded collar;

a first pair of radially extending fan-shaped projections on a lower end of the spindle that are aligned with a second pair of radially extending fan-shaped projections on a lower end of the spring-loaded collar to extend through a mounting hole of a rotary mower blade; the spring-loaded collar rotatable to move the second pair of fan-shaped projections 90 degrees out of alignment with the first pair of fan-shaped projections to clamp the rotary mower blade between the first pair of fan-shaped projections and the spring-loaded collar.

6. The quick attach rotary mower blade system of claim 5 wherein the spring-loaded collar includes a plate from which the first and second pairs of fan-shaped projections extend downwardly.

7. The quick attach rotary mower blade system of claim 6 further comprising a circumferential shoulder around the spring-loaded collar.

8. The quick attach rotary mower blade system of claim 5 wherein the spring-loaded collar includes an upwardly facing cavity and a coil spring in the cavity.

9. The quick attach rotary mower blade system of claim 5 wherein the rotary mower blade mounting hole has a circular center opening and a pair of radially extending fan-shaped openings.

10. A quick attach rotary mower blade system, comprising:

a mower blade with a mounting hole having a circular center opening and a pair of fan-shaped openings extending radially outwardly from the opening, the mounting hole sliding onto a vertical spindle having a first pair of fan-shaped projections and a spring loaded collar with a second pair of fan-shaped projections;

the mower blade compressing a spring in the spring-loaded collar, and rotating along with the spring-loaded collar to move the second pair of fan-shaped projections out of alignment with the first pair of fan-shaped projections which remain in place under the mower blade; and

the spring urging the spring-loaded collar and the second pair of fan-shaped projections into a pair of gaps between the first pair of fan-shaped projections to clamp the mower blade to the vertical spindle.

11. The quick attach rotary mower blade system of claim 10 wherein the spring-loaded collar includes a vertical bore through which the spindle extends, a cavity with a plate where the spring is positioned, and a circumferential outer shoulder adjacent the plate.

12. The quick attach rotary mower blade system of claim 10 further wherein the mower blade rotates 90 degrees to position the second pair of fan-shaped projections into the pair of gaps between the first pair of fan-shaped projections.