Impact absorber for rotary mower blade

Claim 2

A cutting blade arrangement for a mower of the rotary type comprising: a. an elongate blade disposed in a substantially horizontal plane and having formed therein at its mid point an aperture through which a significantly smaller rotatable shaft extends downwardly therethrough, said aperture having a shape such that its longitudinal cross section is of decreasing length as the transverse distance from the center of the aperture is increased; b. a resilient spacer element disposed in said aperture between said shaft and said blade, said spacer having its control portion conforming substantially to and closely surrounding said shaft, each of its longitudinal sides impinging against said blade at at least two points, and each of its transverse sides impinging against said blade at two displaced points with that portion of said spacer between said two displaced points being spaced from said blade to define a cavity; and c. means for securing said blade to said shaft for mutual rotation therewith whereby when the rotation of said blade is interrupted by contact with a relatively immovable object, the resulting shear stress causes said spacer to deform and tend to fill said cavity adjacent the side of the blade with which contact is made.

Claim 3

A cutting blade arrangement as set forth in claim 1 wherein said aperture is diamond-shaped with its opposite vertices aligned in the longitudinal and transverse planes.

Claim 4

A cutting blade arrangement as set forth in claim 2 wherein said spacer element is a truncated diamond in shape, having its transverse vertices removed to provide said cavities.

Claim 5

A cutting blade arrangement as set forth in claim 1 wherein said spacer element is substantially rectangular in shape with its sides aligned in the longitudinal and transverse planes respectively.

Claim 6

A cutting blade arrangement as set forth in claim 1 wherein said spacer element is substantially round in shape.

Claim 7

A cutting blade arrangement as set forth in claim 1 wherein said aperture is hexagon-shaped with a pair of sides aligned in the transverse plane, and further wherein said spacer element is rectangular in shape and is disposed with two sides in contiguous relationship with said aligned sides.

Claim 8

A cutting blade arrangement as set forth in claim 1 wherein said aperture is substantially round in shape.

Claim 9

A cutting blade as set forth in claim 7 wherein said spacer element is substantially square in shape with its sides aligned in the longitudinal and transverse planes respectively.

Claim 10

A cutting blade as set forth in claim 1 wherein said aperture is substantially oval in shape and aligned with its longer axis in the transverse plane.

Claim 11

A cutting blade as set forth in claim 1 wherein the thickness of said spacer is substantially equal to the thickness of said blade.

Claim 12

A cutting blade arrangement as set forth in claim 1 wherein said securing means comprises: a. a hub secured to said shaft above said blade with its lower surface in frictional engagement with said blade; b. a hub plate secured to said shaft below said blade with its upper surface in frictional engagement with said blade; and c. means for biasing said hub and said plate together to frictionally engage said blade for mutual rotation therewith.

Claim 13

A cutting blade arrangement as set forth in claim 11 wherein said hub is secured from relative rotation on said shaft by a key disposed therebetween.

Claim 14

A cutting blade arrangement as set forth in claim 12 and including a fibre washer disposed in close-fit Relationship between said blade and each of said hub and said plate.

Claim 15

A cutting blade arrangement for a mower of the rotary type comprising: a. a shaft extending downwardly for rotation on a substantially vertical axis; b. a hub secured to the lower end of said shaft for rotation therewith said hub having a substantially planar bottom portion; c. an elongate blade disposed in a substantially horizontal plane with its upper surface engaging said hub bottom portion, said blade having formed therein at its midpoint an aperture with a shape such that its longitudinal cross section is of decreasing length as the transverse distance from the center of the aperture is increased; d. a resilient spacer element disposed in said aperture said spacer having a central hole formed therein and having each of its longitudinal sides impinging against said blade at at least two points, and each of its transverse sides impinging against said blade at two displaced points with that portion of said spacer between said two displaced points being spaced from said blade to define a cavity; e. a hub plate disposed below said blade with its upper surface in frictional contact with said blade, said plate having a central hole formed therein; f. and a bolt extending upwardly through said plate and spacer central holes to the core of said shaft, thereby biasing the combination of said shaft, hub, blade, spacer and hub plate into an integral rotatable unit.

Claim 16

A cutting blade arrangement for a mower of the rotary type comprising: a. a shaft extending downwardly for rotation on a substantially vertical axis; b. a hub secured to the lower end of said shaft for rotation therewith said hub having a substantially planar bottom portion; c. an elongate blade disposed in a substantially horizontal plane with its upper surface engaging said hub bottom portion, said blade having formed therein at its midpoint an aperture with a shape such that its longitudinal cross section is of decreasing length as the transverse distance from the center of the aperture is increased; d. a resilient spacer element disposed in said aperture said spacer having a central hole formed therein and having each of its longitudinal sides impinging against said blade at at least two points, and each of its transverse sides impinging against said blade at two displaced points with that portion of said spacer between said two displaced points being spaced from said blade to define a cavity; e. a hub plate disposed below said blade with its upper surface in frictional contact with said blade, said plate having a central hole formed therein; f. and a bolt extending upwardly through said plate and spacer central holes to the core of said shaft, thereby biasing the combination of said shaft, hub, blade, spacer and hub plate into an integral rotatable unit.