Lawn mower including improved blade clutch and brake features

A lawn mower including a cutting blade brake and clutch which discourages blade engagement after a predetermined level of blade brake wear, damage, or improper adjustment is encountered. Also provided is an improved idler pulley system providing an improved "serpentine" belt path therebetween.

TECHNICAL FIELD 
This invention relates in general to drive systems for lawn mowers or other 
powered vehicles, and particularly relates to a belt-driven lawn mower 
blade drive system including improved blade brake and clutch features. 
BACKGROUND OF THE INVENTION 
In the field of powered-driven vehicles such as lawn mowers, it is known to 
provide various belts and pulleys in order to transfer power from one 
rotating shaft, such as an engine drive shaft, to another rotating shaft, 
such as a shaft holding a grass cutting blade or other driven element. 
Examples in the prior art of such systems are as shown in U.S. Pat. Nos. 
4,058,957, 4,300,332, 4,307,558, and 4,409,779. 
In such systems, due to the preference for rubber or other elastomeric 
belts, some provision must be given for stretch or wear of the belts. If 
such a provision is not made, the belt may become loose or disengaged from 
its supporting pulleys. Furthermore, if the belt is to be selectively 
clutched and declutched by a drive pulley to provide selection power 
transfer through the belt, some provision can be made to allow selective 
slippage of the belt relative to the drive pulley. Finally, as brakes are 
often used in such configurations a need always exists to provide improved 
brake performance. 
In reference to U.S. Pat. No. 4,058,957, it may be seen that a belt 27 is 
used to transfer power from a drive pulley 31 to a driven pulley 29, both 
rotating about substantially parallel axes which are fixed relative to the 
mower frame. An idler pulley 33 is pivotably attached relative to the 
mower frame, and provides the function of taking up slack in the belt 
caused by wear or heat, and also the. clutching function described above. 
In reference to U.S. Pat. No. 4,300,332 assigned to McDonough Power 
Equipment, as may be seen, a driven blade pulley 30 is driven by a belt 32 
which is driven by an unshown engine pulley. An idler pulley 34 provides 
the belt take-up and clutching function described above. A part of FIG. 1 
is included in the present application as FIG. 6, denoted as "PRIOR ART". 
In comparison, U.S. Pat. Nos. 4,307,358 and 4,409,779 disclose the use of a 
two-pulley design, in which a movable idler pulley 87 provide the take-up 
and clutching functions described above, with a second pulley having 
independently rotatable or "split" sheaves 35, 51, such that engagement of 
the belt causes the two sheaves 35, 51, to move together by being clutched 
by the belt 85. 
Although some of the above-referenced prior art systems have advantages, 
shortcomings still exist, namely with respect to the ability of prior art 
systems to take up excessive slack in a belt, or to discourage further use 
of the clutching mechanism after a blade brake becomes unacceptably worn. 
SUMMARY OF THE INVENTION 
In summary, the present invention provides advantages over the known prior 
art in that a drive configuration is provided which automatically locks in 
a "blade declutched" position, if a certain amount of brake wear, damage, 
or improper adjustment is encountered. Furthermore, a pair of idler 
pulleys, positioned on opposing sides of the belt path, are provided which 
combine to create a "serpentine" belt path which is more efficient in 
taking up slack in the belt. Therefore, more belt stretching may be 
accommodated. Other advantages are discussed in the detailed discussion 
below. 
Therefore, it is an object of the present invention to provide an improved 
riding or walk-behind lawn mower. 
It is a further object of the present invention to provide a lawn mower 
having an improved blade clutch and brake system. 
It is a further object of the present invention to provide a lawn mower 
having an improved blade clutch and brake system which is simple in 
operation. 
It is a further object of the present invention to provide an improved 
blade clutch and brake mechanism which is simple in construction. 
It is a further object of the present invention to provide an improved 
blade clutch and brake mechanism which is simple in maintenance. 
It is a further object of the present invention to provide an improved 
blade clutch and brake mechanism which accommodates a greater degree of 
belt wear. 
It is a further object of the present invention to provide an improved 
blade clutch and brake mechanism which accommodates a greater degree of 
belt stretching. 
It is a further object of the present invention to provide an improved 
blade clutch and brake mechanism which restricts the operation of a blade 
clutch upon unacceptable brake wear. 
Other objects, features, and advantages of the present invention will 
become apparent upon reading the following detailed description of the 
preferred embodiment of the invention when taken in conjunction with the 
drawing and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is now made to FIGS. 1-5. As may be understood, this invention 
illustrates several top plan views of a blade brake/clutch system 10 which 
includes the use of four pulleys, a cutting blade pulley 20, a first idler 
pulley 22, a second idler pulley 24, and a drive or engine pulley (not 
shown), all of which define a continuous endless path for a belt 26. By 
movement of the idler pulleys, the belt 26 may selectively clutch or 
release (declutch) the belt to allow power to be transferred via the belt 
from an internal combustion or other suitable engine 40 (generally shown 
in FIG. 5) to a rotating cutting blade 42, which is attached to a vertical 
shaft along with the blade pulley. The vertical blade shaft is rotatably 
mounted relative to the cutting blade housing 44, which is suspended or 
otherwise attached relative to the frame of the mower 41 as known in the 
art. 
As in previous prior art systems such as shown in FIG. 6, the first idler 
pulley 22 is rotatably mounted to a brake bar 25, which is rotatably 
mounted about a fixed point "P", about which the blade pulley is also 
rotatably mounted. As the brake bar is rotated clockwise about point "P" 
(see particularly FIG. 4), the brake is applied by a brake band/drum 
configuration including a brake band 27 and a brake drum 28. The flexible 
brake band 27 has one end attached to a point stationary relative to point 
"P", and a second end attached to the brake band. As the brake bar 25 is 
pivoted about point "P" in direction "B", the brake is applied. Pivoting 
in the opposite direction releases the brake. However, unlike the known 
prior art, an additional idler pulley 24 is provided along with associated 
supporting linkages elements 30, 32. This additional pulley 24 provides a 
"serpentine" path for the belt as shown in FIG. 1, which as may be seen 
takes up more slack than a single-idler-pulley configuration shown in FIG. 
5. 
The pair of linkage elements, a pivot bar 30 and a link rod 32 provide a 
novel clutch lock-out feature due to the "jackknife" configuration 
illustrated especially in FIGS. 2 and 3. 
As may be seen, if the brake bar 25 is allowed to travel excessively 
clockwise during the braking mode, the linkages will "lock" into the 
configuration of FIG. 3, with the assistance of a lock spring 33 or other 
suitable device. At this point they can be manually unlocked if so 
desired, but they cannot be unlocked by simply attempting to clutch the 
belt. Excessive clockwise movement of the brake bar may be caused by brake 
wear, brake failure, or improper brake adjustment. 
In particular reference to FIGS. 1-3, it may be seen that the (floating) 
pivot point between the pivot bar 30 and the link rod is spaced apart or 
"offset" relative to the rotational axis of the second idler pulley 24 as 
it rotates relative to the pivot bar 30. This offset may be varied as 
needed to provide a different mechanical advantage as desired. 
As may be seen, the present invention provides improvements over the prior 
art by providing an improved lawn mower cutting blade brake and clutch 
system which discourages use of the cutting blade if the brake is 
improperly operating, and provides improved belt path characteristics 
allowing for improved belt slack take-up cause by belt wear stretch. 
While this invention has been described in specific detail with reference 
to the disclosed embodiments, it will be understood that many variations 
and modifications may be effected within the spirit and scope of the 
invention as described in the appended claims.