Centrifugal clutch and brake for lawn mower

Abstract

An apparatus which automatically prevents the rotation of a rotary blade or the like when a power plant is operating at idling speed and which drivingly engages the rotary blade when the power plant is driven at a predetermined speed which is greater than idling speed. The apparatus includes a housing having a generally frusto-conical portion and a brake shoe which engages a fixed brake band under spring pressure when the power plant is at idling speed and a plurality of weights which move outwardly by centrifugal action into engagement with the housing to move the housing away from the brake shoe and provide a drive connection to a rotary blade when the speed of rotation of the power plant is increased a predetermined amount.

We claim: .[.1. A centrifugal clutch and brake apparatus for selectively connecting a rotatable driven element to a power plant having a drive shaft and which is mounted on a support comprising engaging means carried by the drive shaft of the power plant, return means urging said engaging means toward the axis of the shaft, said return means retracting said engaging means when the power plant is operated at idling speed and permitting said engaging means to be extended by centrifugal action when the power plant is operated at operating speed, said engaging means having a first frictional surface, a housing mounted for rotational and axial movement on the drive shaft of the power plant, said housing including a portion having a second frictional surface which normally is in spaced relationship with said first frictional surface, said housing having first brake means, second brake means fixed to the power plant support, means normally urging said first brake means into engagement with said second brake means, whereby when the drive shaft of the power plant is rotating at idling speed, said engaging means is retracted and said first and second brake means are in engagement with each other, and when the drive shaft is rotating at operating speed, said engaging means is extended so that said first frictional surface is extended into engagement with said second frictional surface of said housing and moves said first brake means out of engagement with said second brake means and causes said housing to be rotated substantially at the speed of rotation of the drive shaft..]. 
     
           .[.A.]. .Iadd.A lawn mower apparatus comprising a support housing having a deck, a power plant mounted on said deck, said power plant being operable at operating and idling speeds and having a drive shaft extending below said deck, a rotatably blade element disposed below said deck, .Iaddend.centrifugal clutch and brake .[.apparatus.]. .Iadd.means .Iaddend.for selectively connecting .[.a.]. .Iadd.said .Iaddend.power plant .[.mounted on a support and having a drive shaft,.]. to .Iadd.said blade element, .Iaddend..[.a rotatable driven element comprising.]. retainer means fixed to .[.the.]. .Iadd.said .Iaddend.drive shaft .[.of the power plant.]., .Iadd.said retainer means having flange means extending outwardly of said drive shaft, .Iaddend..[.a plurality of weights.]. .Iadd.weight means .Iaddend.slidably carried by said retainer means .Iadd.so as to be movable outwardly with respect to said drive shaft, .Iaddend.return means connected to said .[.weights.]. .Iadd.weight means .Iaddend.and urging said .[.weights.]. .Iadd.weight means .Iaddend.toward the axis of said retainer means, said return means retracting said .[.weights.]. .Iadd.weight means .Iaddend.when .[.the.]. .Iadd.said .Iaddend.power plant is operated at idling speed and permitting said .[.weights.]. .Iadd.weight means .Iaddend.to be extended by centrifugal action when .[.the.]. .Iadd.said .Iaddend.power plant is operated at operating speed, each of said .[.weights.]. .Iadd.weight means .Iaddend.having a first .Iadd.tapered .Iaddend.frictional surface adjacent to the end which is remote from the axis of said retainer means, a housing mounted for rotational and axial movement on .[.the.]. .Iadd.said .Iaddend.drive shaft of the power plant, said housing including .[.a.]. .Iadd.first and second portions, said first .Iaddend.portion having a second frictional surface which is in spaced relationship with said first friction surface.[., said housing having.]. .Iadd.and a .Iaddend.first brake means.Iadd., said second frictional surface being of a configuration to permit a relative vertical movement between said first and second frictional surfaces as such surfaces engage one another, means for drivingly connecting said second portion of said housing to said blade element so that said blade element moves concurrently with said housing, .Iaddend.second brake means fixed to said .[.power plant support.]. .Iadd.deck, said first and second brake means being vertically spaced from said first and second frictional surfaces, .Iaddend.means normally urging said first brake means into engagement with said second brake means, whereby when .[.the.]. .Iadd.said .Iaddend.drive shaft of .[.the.]. .Iadd.said .Iaddend.power plant is rotating at idling speed, said .[.weights.]. .Iadd.weight means .Iaddend.are retracted into said retainer means and said first and second brake means are in engagement with each other and when the drive shaft is rotating at operating speed, said .[.weights.]. .Iadd.weight means .Iaddend.are extended into engagement with said .Iadd.second .Iaddend.frictional surface of said .Iadd.first portion of said .Iaddend.housing and move said first brake means out of engagement with said second brake means and cause said housing to be rotated substantially at the speed of rotation of .[.the.]. .Iadd.said 
     
     
        .Iaddend.drive shaft. 3. The invention of claim 2 in which said return means is a substantially continuous spring member, and each of said .[.weights.]. .Iadd.weight means .Iaddend.has .Iadd.an upper and lower surface, and .Iaddend.a recess .Iadd.formed in said upper surfaces of said weight means .Iaddend.which receives a portion of said spring member. .[.4. The invention of claim 2 in which said first and second frictional 
     
     
        surfaces are generally complementary to each other..]. 5. The invention of claim 2 in which said .[.first brake means and.]. .Iadd.upper portion of said housing is generally frusto-conical in configuration and said first brake means being an upper flange portion which extends therefrom, .Iaddend.said second brake means .[.are.]. .Iadd.being .Iaddend.generally flat and .[.are.]. disposed generally normal to the axis of said retainer 
     
     
        means. 6. The invention of claim 2 in which said first brake means and said second brake means are of frusto-conical configurations.Iadd., said first brake means being generally coextensive with said frictional surface 
     
     
        of said first portion of said housing.Iaddend.. 7. In a rotary lawn mower having .Iadd.a support housing with .Iaddend.a deck, a power plant mounted on the deck, a power plant drive shaft extending through an opening in the deck, .Iadd.said power plant being operable to rotate said drive shaft between an operating speed and a slower idling speed, .Iaddend.and a rotatable cutter blade located below said deck .[.and.]. .Iadd.the .Iaddend.improvement comprising a centrifugal clutch selectively connecting said drive shaft to said cutter blade, said clutch including retainer means fixed to said drive shaft, said retainer means having a hub connected to spaced outwardly extending flanges, at least one of said flanges including guide means, a plurality of weights carried by said retainer means and slidably engagable with said guide means, each of said weights having a recess, a substantially continuous return spring means disposed within the recesses of said weights and urging said weights toward said hub of said retainer, said return spring means having a predetermined tension which retracts said weights when said drive shaft is rotated at idling speed and permits said weights to be extended by centrifugal action when said drive shaft is rotated at operating speed, each of said weights having a tapered contact surface remote from said hub, a housing having a body mounted for rotational and axial movement .[.on.]. .Iadd.over .Iaddend.said drive shaft, said housing having a portion fixed to one end of said body and extending outwardly therefrom, said portion having a frusto-conical contact surface which is generally complementary with said contact surfaces of said weights .Iadd.and is of a size to extend beyond said contact surfaces of said weights .Iaddend.and .Iadd.which is .Iaddend.normally .[.being.]. in spaced relationship therewith, said housing having cutter blade mounting means at the opposite end of said body .Iadd.for mounting said cutter blade thereto, .Iaddend.brake means including brake shoe means fixed to said housing, brake band means fixed to said deck, and brake spring means normally urging said brake shoe means into intimate engagement with said brake band means, whereby when said drive shaft is rotating at idling speed said weights are retracted by said return spring means and said brake shoe means engages said brake band means and whens said drive shaft means is rotating at operating speed, said weights are extended by centrifugal action so that said tapered surfaces of said weights engage said contact surface of said housing and move said brake shoe out of engagement with said brake band means and cause said housing to be rotated substantially at the speed of rotation of said drive shaft. .Iadd.8. A lawn mower apparatus comprising a support housing having a deck, a power plant operable between an operating speed and an idling speed supported relative to said deck, said power plant having a drive shaft having a lower portion extending downwardly through said deck, and cutter blade element disposed below said deck, a centrifugal clutch and brake means for selectively connecting said cutter blade element to said power plant, said clutch and brake means including movable engaging means spaced below said deck of said lawn mower housing, guide means for drivingly connecting said engaging means to said drive shaft of said power plant, return means urging said engaging means toward the axis of said drive shaft, said return means retracting said engaging means when said power plant is operated at idling speed and permitting said engaging means to be extended from said drive shaft when said power plant is operated at operating speed, said engaging means having a first frictional surface, a housing mounted for rotational and axial movement about the drive shaft, said housing having upper and lower portions, said lower portions of said housing including a cylindrical body which surrounds and is in spaced relationship to said lower portion of said drive shaft, said lower portion of said housing having means for mounting said blade element adjacent the lowermost end thereof, said upper portion of said housing extending upwardly with respect to said lower portion thereof and having upwardly extending side walls which extend beyond said engaging means toward said deck of said lawn mower housing and which have inner surfaces defining a cavity therebetween, said engaging means being disposed within said cavity, said inner surface of said side walls of said housing having a second frictional surface which is selectively engaged by said first frictional surface of said engaging means, said upper portion of said housing having a first braking surface which is disposed between said second frictional surface and the lawn mower housing, second brake means carried by the lawn mower housing and means for continuously urging first braking surface of said housing toward engagement with said second brake means, whereby when said drive shaft of said power plant is rotating at idling speed, said engaging means is retracted and said first braking surface is in engagement with said second brake means, and when said drive shaft is rotating at operating speed, said engaging means is extended so that said first frictional surface is extended into engagement with said second frictional surface of said inner surface of said side wall of said housing and moves said housing out of engagement with said second brake means and causes said housing to be rotated substantially at the speed of rotation of said drive shaft. .Iaddend. .Iadd.9. The invention of claim 8 in which said first braking surface of said housing includes an annular generally planar flange member which extends outwardly from said side walls of said upper portion of said housing, said second brake means including a generally flat band which is fixed to the lawn mower housing and extends generally parallel to said first brake means. .Iaddend. .Iadd.10. The invention of claim 8 in which said guide means includes a hub which is connected to said drive shaft, first and second outwardly extending flange means disposed adjacent opposite ends of said hub and being generally parallel with one another, rib means carried by said first flange means and extending outwardly so as to be in generally perpendicular relationship with said drive shaft, said engaging means being positively guided by said rib means between said first and second 
     
     
        flange means of said guide means. .Iaddend. .Iadd.11.  The invention of claim 8 in which said second brake means is mounted to said deck of said lawn mower housing so as to extend downwardly therefrom so as to engage said first braking surface of said housing, said first braking surface of said upper portion of said housing being disposed along a portion of said inner surface of said side walls of said housing. .Iaddend.