Electric Motor and Blade Assembly for a Lawn Mower

Abstract

An assembly for protecting components of an electric motor on a lawn mower deck includes a shaft connected at opposite ends to the motor rotor and a blade adapter. The blade adapter is interconnected to a cutting blade. A blade mounting gap is defined between a shoulder of the blade adapter and a head of a fastener that secures the blade to the shaft. A biasing member is captured within the blade mounting gap and frictionally couples the blade and the shaft for rotation together. The blade slips with respect to the shaft in response to the blade encountering a force that overcomes the blade coupling friction.

What is claimed is: 
     
         1 . An assembly comprising:
 an electric motor having a rotor and a stator;   a shaft having first and second opposite ends, the first end being interconnected to the rotor for rotation with the rotor;   a blade;   a blade adapter mounted to the second end of the shaft, the blade adapter including a shoulder having a shoulder diameter and a stand-off portion having a smaller diameter than the shoulder diameter, the stand-off-portion extending from the shoulder to a free end;   a fastener securing the blade to the free end of the blade adapter, the fastener including a head, wherein a blade mounting gap is defined between the shoulder and the fastener head; and   a biasing member captured within the blade mounting gap and being deflected within the blade mounting gap a predetermined amount to generate a biasing force to generate a blade coupling friction to frictionally couple the blade and the shaft for rotation together;   wherein the blade slips with respect to the shaft in response to the blade encountering a force that overcomes the blade coupling friction.   
     
     
         2 . The assembly of  claim 1 , wherein the blade is captured in the blade mounting gap with the biasing member. 
     
     
         3 . The assembly of  claim 2 , wherein the blade is between the biasing member and the blade adapter shoulder. 
     
     
         4 . The assembly of  claim 1 , wherein the blade adapter is formed in a geometry that allows the blade adapter to engage with the shaft to couple the blade adapter and shaft for rotation together. 
     
     
         5 . The assembly of  claim 1 , wherein the second end of the shaft is tapered and the blade adapter includes a tapered aperture that receives the tapered second end of the shaft for a friction fit between the second end of the shaft and the blade adapter. 
     
     
         6 . The assembly of  claim 1 , wherein:
 the fastener extends through the blade, blade adapter, and biasing member;   the fastener connects to the second end of the shaft; and   the fastener head applies a force to the blade and biasing member directed toward the shoulder of the blade adapter, the force causing the biasing member to deflect within the blade mounting gap.   
     
     
         7 . The assembly of  claim 1 , wherein the fastener threads into the second end of the shaft. 
     
     
         8 . The assembly of  claim 1 , wherein the biasing member extends around the stand-off portion. 
     
     
         9 . The assembly of  claim 1 , wherein the biasing member comprises a spring washer. 
     
     
         10 . A blade assembly comprising:
 a shaft;   a blade having opposite sides;   a blade mounting fastener;   a biasing member;   a first bearing surface coupled for rotation with the shaft;   a gap setting component; and   a second bearing surface, wherein   the first and second bearing surfaces are positioned on the opposite sides of the blade,   the gap setting component dictates a blade mounting gap when the assembly is tightened,   the gap setting component prevents the blade mounting fastener from narrowing the blade mounting gap beyond a preferred gap size,   the biasing member is deflected in response to the blade mounting gap being narrowed to the preferred gap size, and   in response to being deflected, the biasing member generates a blade coupling force which gives rise to a blade coupling friction to frictionally couple the blade and the first bearing surface to cause the blade and shaft to rotate together.   
     
     
         11 . The blade assembly of  claim 10 , wherein the blade coupling friction arises directly between the blade and the first bearing surface. 
     
     
         12 . The blade assembly of  claim 10 , wherein the blade coupling friction arises between the blade and the first bearing surface indirectly through a component between the blade and the first bearing surface. 
     
     
         13 . The blade assembly of  claim 10 , wherein the gap setting component comprises a stand-off portion extending from the first bearing surface. 
     
     
         14 . The blade assembly of  claim 10 , wherein the second bearing surface comprises the biasing member. 
     
     
         15 . The blade assembly of  claim 10 , wherein the blade coupling friction comprises a normal force. 
     
     
         16 . The blade assembly of  claim 10 , wherein a blade impact event resists rotation of the blade to overcome the blade coupling friction such that the shaft rotates with respect to the blade. 
     
     
         17 . A lawn mower comprising:
 a chassis supporting a plurality of wheels;   a cutting deck supported by the chassis;   a deck motor electrically coupled to a battery, the deck motor including a housing containing a stator, a rotor, and a shaft extending out of the housing, the deck motor attached to the cutting deck so that at least a portion of the shaft extends under the cutting deck; and   a blade coupled to the shaft and configured to rotate under the cutting deck when the deck motor rotates the rotor and shaft;   wherein relative rotation between the blade and the shaft occurs in response to a torque on the blade exceeding a threshold value.   
     
     
         18 . The lawn mower of  claim 17 , wherein the relative rotation between the blade and the shaft occurs by overcoming a frictional engagement between the blade and the shaft. 
     
     
         19 . The lawn mower of  claim 17 , further comprising:
 a fastener mounting the blade to the shaft; and   a biasing member deflected by the fastener to generate the frictional engagement.   
     
     
         20 . The lawn mower of  claim 19 , further comprising a blade adapter including a shoulder and a stand-off portion extending from the shoulder to a free end, wherein:
 the fastener includes a fastener head;   the fastener mounts the blade adapter to an end of the shaft with the stand-off portion extending toward the fastener head;   a blade mounting gap is defined between the shoulder and the fastener head; and   the blade and biasing member are captured in the blade mounting gap.   
     
     
         21 . The assembly of  claim 20 , wherein the blade is between the biasing member and the blade adapter shoulder. 
     
     
         22 . The assembly of  claim 20 , wherein:
 the fastener extends through the blade, blade adapter, and biasing member; and   the fastener head directly or indirectly applies a force to the blade directed toward the shoulder of the blade adapter.   
     
     
         23 . The assembly of  claim 21 , wherein the fastener threads into the second end of the shaft. 
     
     
         24 . The assembly of  claim 21 , wherein the biasing member extends around the stand-off portion. 
     
     
         25 . The assembly of  claim 21 , wherein the biasing member comprises a spring washer.