Mulching mower

A mulching lawn mower has a closed cutting chamber in a mulching mode such that the grass clippings are confined within the cutting chamber except for when they fall out through the open bottom face of the chamber. The cutting chamber has a first portion of toroidal or doughnut form generally closely surrounding the blade tips. In addition, the front portion of the cutting chamber includes a forwardly protruding wedge-shaped extension having side walls that converge towards one another in a pie-shaped fashion. The wedge-shaped extension further includes a top wall that extends between the side walls. This top wall is sloped or inclined downwardly as it extends to the front of the mower such that the height of the wedge-shaped extension gradually decreases until the wedge-shaped extension disappears at its front edge. The wedge-shaped extension reduces power consumption of the mower when the mower is placed in its mulching mode and is used to mulch grass.

TECHNICAL FIELD 
This invention relates to a rotary lawn mower having a cutting chamber 
which is shaped for efficiently mulching the grass clippings while 
reducing the power consumption of the mower. 
BACKGROUND OF THE INVENTION 
Mulching lawn mowers are known which direct the grass clippings severed by 
the cutting blade downwardly out of the cutting chamber to deposit such 
clippings in the standing grass remaining in the cut grass path. Various 
kinds of such mulching mowers are known. For example, mulching mowers are 
disclosed in U.S. Pat. Nos. 4,205,512 and 4,951,449 to Thorud, both of 
which are assigned to the assignee of this invention. 
The mulching mowers shown in the Thorud patents have grass deflecting 
members or kickers within the cutting chamber to assist in the downward 
movement of the grass clippings. These kickers comprise angled grass 
deflecting surfaces that are fixed in each cutting chamber above the plane 
of the blade. The grass deflecting surfaces are shaped and positioned to 
intercept the grass clippings as they circulate inside the cutting chamber 
to redirect such clippings downwardly. The kickers are spaced apart around 
the circumference of the cutting chamber. 
Other mulching mowers are known in which no kicker members are present in 
the cutting chamber. Instead, the cutting chamber and blade are specially 
shaped to effect mulching. For example, U.S. Pat. No. 3,085,386 to 
Slemmons discloses a mulching mower having a donut-shaped cutting chamber. 
A specially configured cutting blade allegedly causes the grass clippings 
to be cut in a radial outer portion of the cutting chamber and to be 
circulated upwardly and inwardly inside the cutting chamber to eventually 
be driven downwardly out of the cutting chamber through a radial inner 
portion of the chamber. 
Many mulching mowers known today circulate a fairly significant halo of 
grass around the cutting chamber until the grass clippings are driven or 
fall downwardly out of the cutting chamber. Many of these mowers, 
including the mulching mowers shown in the above-identified patents, are 
powered by internal combustion engines in which power consumption is not 
generally an issue. Engines of sufficient horsepower are available and can 
generally be used to allow the grass clippings to be mulched without 
bogging down. 
However, mowers powered by electrical motors, or lower horsepower internal 
combustion engines, have certain advantages, including those of reduced 
emissions. In the field of electrically powered mowers, various mowers 
have been introduced having DC motors powered by self-contained, 
rechargeable batteries. Some of these mowers use a generally 
conventionally shaped cutting chamber around the blade, namely a cutting 
chamber that is generally circular and closely surrounds the blade. This 
cutting chamber can be closed over its top and sides in a mulching mode 
such that the grass clippings are mulched by being driven downwardly 
through the open bottom side or face of the cutting chamber. 
The power drain on such electrically powered mowers when they are used to 
mulch is significant. As a practical matter, the batteries may become 
discharged before the entire lawn or other turf area is mowed. This 
requires that the batteries be recharged before the mowing job can be 
finished, which is obviously inconvenient. Thus, the power consumption of 
such mowers during mulching, and the consequent reduction in their run 
time per charge, is a limitation of such a product. 
SUMMARY OF THE INVENTION 
It is one aspect of this invention to provide a mulching lawn mower that is 
an efficient mulcher and exhibits reduced power consumption when mulching. 
These and other aspects of the invention are provided in a mulching rotary 
lawn mower having a cutting blade. A motive means is provided for rotating 
the blade in a plane of rotation about a generally vertical rotational 
axis. A cutting chamber surrounds and encloses the cutting blade over its 
top and sides when mulching. The cutting chamber has an outer 
circumferential wall with a lower peripheral edge located below the plane 
of rotation of the cutting blade. A wedge-shaped extension is provided 
over a portion of the cutting chamber, the wedge-shaped extension being 
formed in part by a portion of the outer circumferential wall that extends 
further radially outwardly from a normal orientation thereof and is sloped 
downwardly as it extends radially outwardly to form an inclined top wall 
of the extension.

DETAILED DESCRIPTION 
Referring to FIG. 1, the mower 2 of this invention includes a mower housing 
4 having a sandwich construction for providing a cost-effective yet strong 
and durable mower 2. This sandwich construction includes: 
a one-piece plastic deck 6, injection molded from an inexpensive, 
lightweight plastic material (e.g. high-density polyethylene), that forms 
the visible superstructure of mower 2; and 
a metallic liner 8, stamped from relatively thin steel (e.g. 20 gauge), 
that forms the cutting chamber 10 and is integrally affixed to plastic 
mower deck 6 to be received within and hidden by plastic mower deck 6. 
Deck 6 and liner 8 will be integrally affixed to one another by a plurality 
of attachment screws 12. When so united to form mower housing 4, the 
combined weight of deck 6 and liner 8 is quite light, on the order of ten 
pounds or so. 
Mower housing 4 is supported for movement over the ground by a plurality of 
rotatable, ground engaging wheels 14, disposed in a pair of front wheels 
14f and a pair of rear wheels 14r. Only one front wheel 14f and one rear 
wheel 14r of each pair are shown in FIG. 1. The front wheels 14f are 
rotatably carried on the opposed ends of a front axle 16f. Similarly, the 
rear wheels 14r are rotatably carried on the opposed ends of a rear axle 
16r. Front and rear axles 16 are supported on mower housing 4 simply by 
being captured or trapped between deck 6 and liner 8 when those two 
components are assembled together to form mower housing 4, as will be 
described in more detail hereafter. 
A motive means 18 is carried on mower housing 4 arranged with its drive 
shaft 20 extending vertically for rotating a cutting blade 22 within 
cutting chamber 10 in mower housing 4. Cutting chamber 10 is configured to 
act as an extremely effective mulcher even with a relatively low power 
motive means 18. Preferably, motive means 18 comprises an electric motor 
24, either a DC motor operated by self-contained batteries (not shown) 
carried in mower housing 4 or an AC motor operated by an external 
electrical AC power source (not shown) coupled to the motor by suitable 
electrical cords (not shown). However, mower 2 of this invention is not 
limited for use with electrical motors, but may also employ an internal 
combustion engine in place of electric motor 24. 
Motor 24 is carried on mower housing 4 within a recessed motor compartment 
26 provided in plastic deck 6. Deck 6 preferably includes a motor shroud 
(not shown) to enclose motor compartment 26 to protect motor 24 and its 
associated electrical components from exposure to the environment. In 
addition, mower 2 includes a U-shaped handle assembly (not shown) 
extending upwardly and rearwardly from mower housing 4 to allow mower 2 to 
be pushed and manipulated by an operator who walks behind mower housing 4. 
Thus, lawn mower 2 of this invention is of the type commonly known as a 
walk behind rotary mower. 
Referring now to the construction of metallic liner 8, liner 8 includes a 
generally toroidal or "doughnut" shaped cutting chamber 10 in which the 
cut grass particles are circulated before they are discharged. This 
cutting chamber 10 is formed by various integrally formed walls including 
an inner circumferential wall 28, a relatively horizontal top wall 30, and 
an outer circumferential wall 32. Inner circumferential wall 28 slopes 
inwardly as it extends downwardly from top wall 30 to its lower end where 
it joins a ring-shaped motor attachment flange 34. Inner circumferential 
wall 28 and motor attachment flange 34 effectively form a pie-shaped 
recess in the central portion of liner 8. Outer circumferential wall 32 
extends generally vertically downwardly from top wall 30 to terminate in a 
lower peripheral edge 36. Outer circumferential wall 32 is considerably 
longer than inner circumferential wall 28 such that its lower peripheral 
edge 36 is located below the plane of rotation of cutting blade 22. 
The toroidal cutting chamber 10 formed in liner 8 is generally flat and of 
relatively constant cross-sectional shape except for two exceptions. 
First, a side discharge opening 38 is provided in outer circumferential 
wall 32 of chamber 10 along one lateral side to allow grass clippings to 
be discharged through that opening 38 to the side of mower 2. Plastic deck 
6 preferably includes a pivotal flap or cover (not shown) that is spring 
biased to normally cover side discharge opening 38 to close this opening 
38 off and to place mower 2 into its mulching mode. In this mulching mode, 
cutting chamber 10 is effectively closed over its sides and its top such 
that the grass clippings can be discharged only through the open bottom 
face of cutting chamber 10. However, if one wishes to discharge the grass 
to the side rather than to mulch, the flap or cover that normally covers 
side discharge opening 38 can be pivoted upwardly to open side discharge 
opening 38 in liner 8. Then, the grass clippings exit through the side of 
liner 8 and through a side discharge chute to fall directly onto the 
ground or into a bagging attachment that may be connected to plastic deck 
6 in communication with side discharge opening 38. 
Side discharge opening 38 extends over a substantial portion of the depth 
of outer circumferential wall 32. This leaves only a small strip 40 of 
steel remaining in that wall underlying side discharge opening 38. Because 
this area of liner 8 is often impacted with rocks or other debris being 
circulated in cutting chamber 10, a separate steel or plastic reinforcing 
rod 42 is attached to liner 8 in that strip area underlying side discharge 
opening 38 to provide adequate strength and durability. Rod 42 is 
configured to nest within a portion of an upturned lip 44 provided on 
lower peripheral edge 36 underlying side discharge opening 38. Lip 44 is 
provided with two tabs 46 that may be bent down to clinch rod 42 in place 
after rod 42 is nested within lip 44. The tabs are shown in FIG. 2 prior 
to being clinched downwardly over rod 42. 
The second exception to the generally uniform shape of the toroidal cutting 
chamber is a forwardly extending, wedge-shaped extension 48 provided in 
liner 8 over a forward portion of cutting chamber 10. Basically, outer 
circumferential wall 32 of deck 6 is pulled forwardly over this area and 
is sloped downwardly as it extends forwardly to form a top wall 50 of 
extension 48. Triangularly shaped side walls 52 join the sloped top wall 
50 of wedge-shaped extension 48 to the normal, curved shape of outer 
circumferential wall 32. Forward wedge-shaped extension 48 decreases in 
depth as it extends forwardly. In addition, side walls 52 of forward 
extension 48 slant inwardly as they extend forwardly such that forward 
extension 48 also decreases in width. 
The purpose of forward wedge-shaped extension 48 is to form a space in 
toroidal cutting chamber 10 of expanded volume to allow the grass 
clippings being circulated in cutting chamber 10 to more quickly leave 
cutting chamber 10 and be mulched. Referring to FIG. 4, the normal 
cross-sectional shape of the toroidal cutting chamber is indicated by the 
dashed line 54. Thus, wedge-shaped extension 48 comprises that space or 
volume forward of dashed line 54, keeping in mind that FIG. 4 is a 
two-dimensional representation of wedge-shaped extension 48 taken along 
the longitudinal centerline of mower 2. Wedge-shaped forward extension 48 
has been found by the Applicants to be particularly desirable in improving 
the mulching efficiency of an electrically powered mower or any mower in 
which the power available for cutting is a concern. 
Referring to FIG. 3, in a mower 2 having a cutting chamber 10 with a 
diameter d of approximately 18 inches, one version of wedge-shaped 
extension 48 giving good results has a maximum width w.sub.1 of 
approximately 11 inches tapering inwardly to a minimum width w.sub.2 of 
approximately 7 inches. Referring to FIG. 6, in a mower 2 having a 
perpendicular distance h of approximately 3.5 inches between lower 
peripheral edge 36 and top wall 30, such an extension has a maximum height 
h at the rear of approximately 2.5 inches and a length 1 along the base of 
side wall 52 of approximately 3.75 inches. In general, the Applicants have 
found that maximizing the volume in extension 48 is desirable within the 
constraints of size imposed by the dimensions of the forward portion of 
mower 2. 
In addition to cutting chamber 10 just described, liner 8 also includes 
front and rear attachment aprons 56 and 58 integrally formed therewith. 
Each of the attachment aprons 56, 58 includes a relatively horizontal 
surface 60 that is spaced a small distance above lower peripheral edge 36 
of cutting chamber 10. Each attachment apron 56, 58 includes a plurality 
of holes 62 through which some of the threaded attachment screws 12 extend 
when joining liner 8 to plastic deck 6. Three such holes 62 are spaced 
across the width of front apron 56. Four such holes 62 are spaced across 
the width of rear apron 58, two holes 62 in a front row and two holes 62 
in a rear row. 
Each of the attachment holes 62 in the rear row on rear apron 58 are not 
formed in the plane of horizontal surface 60 of apron 58 as are holes 62 
in the front row. Rather, the rear attachment holes 62 are carried on the 
front end of forwardly extending fingers 64 that are bent downwardly out 
of relieved portions of apron 58 such that fingers 64 are parallel to 
horizontal surface 60 of apron 58 but are located beneath the relieved 
apron portions. Each finger 64 includes an arcuate groove 66 located 
immediately rearwardly of each rear attachment hole 62. 
This finger construction forms a convenient way of attaching a trailing 
rear shield 68 to mower 2. Shield 68 is molded of a plastic material 
having a cylindrical upper portion 70 forming a pivot rod. This 
cylindrical portion 70 can be received in arcuate grooves 66 on fingers 64 
by pushing cylindrical portion 70 rearwardly in the gap formed between 
fingers 64 and rear apron 58 until cylindrical portion 70 drops into place 
in arcuate grooves 66. Trailing rear shield 68 is provided with slots 72 
to allow fingers 64 to pass through the plane of shield 68 during this 
insertion process. In any event, when trailing rear shield 68 is so 
installed, shield 68 is free to rotate around the axis of its cylindrical 
portion 70, but will be retained on liner 8 by the same two attachment 
screws 12 passing upwardly through attachment holes 62 in fingers 64. 
Thus, mower 2 need not have any separate way of pivotally attaching 
trailing rear shield 68 to liner 8--some of the same attachment screws 12 
that help hold liner 8 to plastic deck 6 retain trailing rear shield 68 in 
place in arcuate grooves 66 formed in fingers 64. 
Turning now to the construction of plastic deck 6, plastic deck 6 is formed 
to substantially wholly enclose and surround steel liner 8 when the two 
are united together. Deck 6 includes a recessed motor compartment 26 that 
has a pie-shaped portion 74 that corresponds in shape to the pie-shaped 
central portion of liner 8. In addition, motor compartment 26 includes a 
flat floor 76 extending rearwardly from pie-shaped portion 74. This flat 
rear floor 76 of motor compartment 26 is used as a battery storage area in 
a mower powered by a DC motor. In any event, when liner 8 and deck 6 are 
joined together, pie-shaped portion 74 of motor compartment 26 nests 
within the similarly shaped pie-shaped portion of liner 8 and rear floor 
76 of motor compartment 26 abuts against a portion of top wall 30 of liner 
8, as shown in FIG. 6. 
Plastic deck 6 includes a raised nose portion 78 defining the front 
exterior surface of mower 2. When deck 6 and liner 8 are assembled 
together, this nose portion 78 is spaced substantially above the front 
portion of cutting chamber 10. However, a plurality of longitudinally 
extending ribs 80 are formed on the undersurface of nose portion 78 
extending downwardly. These ribs 80 have a lower edge shaped to conform to 
the shape of liner 8 so as to abut against various portions of liner 8. 
One such longitudinal rib 80 is shown in FIG. 6 abutting against a portion 
of top wall 30 of liner 8 and wedge-shaped extension 48 of cutting chamber 
10. In addition, similar longitudinal ribs 81 can extend downwardly from 
rear floor 76 of plastic deck 6 to engage against the rear portion of 
cutting chamber 10 and rear apron 58 in selected portions thereof. 
Transverse ribs (not shown) can also extend downwardly from the underside 
of deck 6 to engage against lateral portions of cutting chamber 10. 
The underside of plastic deck 6 is also formed with a plurality of 
downwardly extending bosses 82 each having an interior bore with screw 12 
being self-threading when screwed into such bores. These various bosses 82 
are aligned with attachment holes 62 in liner 8 when deck 6 is 
superimposed on liner 8. Thus, the various attachment screws 12 can extend 
upwardly through attachment holes 62 in liner 8 to be threaded into bosses 
82 on deck 6 to firmly and rigidly secure deck 6 to liner 8. In addition 
to attachment holes 62 provided on the front and rear aprons of liner 8 as 
described previously, various other attachment holes 60 can be provided on 
top wall 30 of cutting chamber 10 to be mated with other bosses (not 
shown) on deck 6. 
As previously described, wheels 14 used to support mower housing 4 are 
carried on the opposed ends of front and rear steel axles 16. Axles 16 are 
conveniently formed as separate components. Some of the ribs 80, 81 on the 
underside of deck 6, as well as the side walls of deck 6, are formed with 
arcuate bearing surfaces 84 in which axles 16 are received. Axles 16 are 
merely placed into such bearing surfaces 84 before liner 8 is joined to 
deck 6. When liner 8 is then screwed to deck 6, the front and rear aprons 
56, 58 thereon hold axles 16 in place in deck 6, i.e. axles 16 are 
captured or trapped between arcuate bearing surfaces 84 in deck 6 and the 
front and rear aprons of liner 8 Thus, axles 16 are easily and 
inexpensively mounted on mower housing 4 due to the sandwich construction 
comprising deck 6 and liner 8. 
Each axle 16 includes an integrally formed circular ring 86 thereon. At 
least some of arcuate bearing surfaces 84 formed in deck 6 are spaced 
apart by a distance slightly greater than the thickness of ring 86 to 
allow ring 86 to be received therein. In addition, the front and rear 
aprons on liner 8 are each provided with a slot 88 for receiving a bottom 
portion of ring 86 when deck 6 and liner 8 are assembled together. This 
ring 86 and its described engagement with deck 6 and liner 8 prevent 
substantial lateral movement of axle 16 relative to mower housing 4 to 
prevent wheels 14 from engaging against the sides of mower housing 4. 
Each axle 16 is normally fixed in place on mower housing 4 through a height 
of cut adjustment mechanism which will be described next. However, axles 
16 are free to rotate relative to mower housing 4 during a height of cut 
adjustment operation to vary the position of wheels 14 relative to the 
housing. Thus, while the deck and liner construction sandwiches or traps 
axles 16 therebetween, they are not trapped so tightly that they cannot 
rotate during a height of cut adjustment operation. However, once the 
height of cut is set to a desired value and that adjustment is locked in 
place, axles 16 are then non-rotatably fixed to mower housing 4 during 
normal operation of mower 2. 
Conventional height of cut adjustment mechanisms are provided for changing 
the height of mower housing 4 relative to the ground. These include a 
height of cut lever 89 formed as a spring arm which is clamped or fixed to 
each axle 16 using the same pivot bolt that rotatably journals one of 
wheels 14 to axle 16. Each height of cut lever 89 carries a pin or button 
90 which is received in one of a plurality of locking recesses 92 formed 
in an arcuate array. The spring bias in lever 89 is normally in the 
direction that keeps locking pin 90 engaged with one of locking recesses 
92 in the array thereof. However, when it is desired to change the height 
of cut, the operator need only pull outwardly on lever 89 to disengage pin 
90 from a first recess 92, to then rotate axle 16 using height of cut 
lever 89 until pin 90 thereon is aligned with a different recess 92, and 
to then release height of cut lever 89 to allow the bias therein to force 
pin 90 into the new recess 92, thus changing the orientation of wheels 14 
relative to mower housing 4 to adjust the height of mower housing 4 
relative to the ground. 
Locking recesses 92 for the front height of cut lever 89 can simply be 
molded into one side wall of plastic deck 6 as only 1/3 of the weight 
carried on deck 6 is at the front of mower 2. However, a separate steel 
plate 94 is used for providing locking recesses 92 on the rear of mower 2, 
where the batteries are stored, to coact with the rear height of cut lever 
89 since 2/3 of the mower's weight is at the rear of mower 2. This plate 
94 can simply be inserted into a slot in a recess 96 formed therefor in 
the side wall of deck 6 with plate 94 again being clamped between deck 6 
and liner 8 when the two are assembled together. In this regard, rear 
apron 58 of liner 8 has an upturned side lip 100 for engaging against the 
outside of the bottom of plate 94 when plate 94 is clamped in place by 
liner 8. Locking recesses 92 at the front and rear of mower 2 and their 
corresponding height of cut levers 89 are desirably provided on only one 
side of plastic deck 6. 
The Applicants have found that mower housing 4 formed by an upper plastic 
deck 6 and a fixedly attached steel liner 8 is inexpensive to produce but 
very rigid and durable during operation. Steel liner 8 withstands impacts 
from rocks and other debris and is not prone to being chipped or damaged 
during use of mower 2. Plastic deck 6 can be inexpensively formed from a 
less expensive plastic and united to steel liner 8, providing a mower 
housing 4 which is less expensive than one which is cast from aluminum or 
one made from a plastic of sufficient durability that it could be used to 
form cutting chamber 10. The nested configuration of the pie-shaped 
portions of deck 6 and liner 8, the abutment of the various surfaces 
therebetween, the use of the front and rear attachment aprons on liner 8, 
all provide a liner 8 which can be easily attached to plastic deck 6 and 
which rigidifies plastic deck 6 to a substantial degree. 
Another advantage of this sandwich construction is the ability to 
conveniently and simply support some of the other components of mower 2 
between deck 6 and liner 8, or on liner 8, when deck 6 and liner 8 are 
joined together. For example, the front and rear axles 16 are simply 
trapped or captured between arcuate bearing surfaces 84 therefor as formed 
in deck 6 and portions of liner 8 and are retained in place simply by 
securing liner 8 to deck 6. Similarly, trailing rear shield 68 simply 
hangs from a portion of liner 8 and is retained in place by some of the 
same attachment screws 12 which join deck 6 and liner 8 together. This 
contributes to the cost effectiveness of mower housing 4. 
In addition, it is possible to easily change the styling or look of mower 
2, or to have different looks for different models of mowers, simply by 
having differently shaped plastic decks 6 that can be joined to a common 
liner 8. Again, this contributes to manufacturing efficiency and to the 
cost effectiveness of mower 2. 
As noted previously and as shown in FIG. 6, mower 2 is preferably equipped 
with a DC motor. One such motor that can be used is a 24 V DC motor having 
approximately 0.68 peak horsepower, though a 36 V DC motor could also be 
used. Motor 24 is received in the central portion of mower housing 4 and 
specifically in the nested pie-shaped portions of plastic deck 6 and liner 
8. Motor 24 includes a flat attachment bracket 102 on the bottom thereof 
which rests on a ring 104 carried at the bottom of pie-shaped portion 74 
on plastic deck 6. A plurality of bolts extend up through motor attachment 
flange 34 on liner 8 and through ring 104 on deck 6 to bolt electric motor 
24 in place. 
Electric motor 24 includes a vertically downwardly extending drive shaft 
20. The lower end of drive shaft 20 includes an internally threaded bore. 
A bushing 106 is received around drive shaft 20 and a bolt 108 is used to 
clamp cutting blade 22 against the bottom of bushing 106, bolt 108 being 
threaded into and tightened in the bore on the lower end of drive shaft 
20. A fan 110 is not-rotatably received on bushing 106, e.g. by a 
polygonal fit between the two, to rotate with bushing 106 and hence with 
blade 22. Fan 110 helps cool electric motor 24. 
Cutting blade 22 received in cutting chamber 10 includes a relatively flat 
central portion 112 and downwardly sloped radial outer portions 114. Each 
radial outer portion includes an upturned sail 116 at its radially outer 
end along the trailing edge of blade 22, tipped up at 15.degree. relative 
to the horizontal. A sharpened cutting edge 118 is located in the 
downwardly sloped outer blade portions 114 along the leading blade edge 
which cutting edge 118 has a length generally equal to or slightly less 
than the normal cross-sectional width of toroidal cutting chamber 10. As 
blade 22 is rotated by operation of motor 24 in a generally horizontal 
cutting plane, cutting edges 118 sever grass and circulate the cut grass 
clippings in cutting chamber 10 in the direction of rotation of the blade. 
Basically, the grass clippings form a rotating mass or halo of clippings 
carried in cutting chamber 10. 
The Applicants have found that use of the forwardly extending wedge-shaped 
extension 48 of cutting chamber 10 significantly reduces the power 
consumption of an electrically powered mower. This is thought to be due to 
the relative quickness in which the clippings exit cutting chamber 10. 
Rather than continually circulating the clippings in a large mass around 
and around cutting chamber 10 until they fall out of the open bottom face 
of cutting chamber 10, the clippings more quickly fall out of cutting 
chamber 10 when they reach wedge-shaped extension 48 and the expanded 
volume contained therein. This is assisted by the downward slope of top 
wall 50 of extension 48 which mechanically deflects the clippings 
downwardly out of cutting chamber 10 and into the grass. While some of the 
clippings may be picked up and recut again when mower 2 passes over them 
since they are deposited in advance of cutting blade 22, at least some 
will be hidden in the grass after their first pass through wedge-shaped 
extension 48. Thus, the blade does not have to circulate as large a mass 
of clippings as it would if wedge-shaped extension 48 were absent and the 
front of cutting chamber 10 had the same cross-sectional toroidal shape as 
the rest of cutting chamber 10. 
The practical effect of this wedge-shaped extension 48 of cutting chamber 
10 is that the amperage draw on electric motor 24 is considerably less 
than in a mower without this extension. In a battery powered mower having 
a DC motor 24, this translates into a longer run time for mower 2 given 
the same battery charge. This is a significant advantage. 
The Applicants have tested a mower 2 of this invention having forward 
wedge-shaped extension 48 powered by a 24 V DC motor against a competitive 
electrically powered mower utilizing a similar 24 V DC motor and battery 
power. In a test of free run time, i.e. how long a full charge will be 
depleted by operation of the motor while running freely without cutting 
grass, the mower 2 of this invention had an average free run time of 114 
minutes versus an average free run time of 100 minutes for the competitive 
mower. However, in a test of run time while cutting 1 inch of grass and 
mulching the clippings, the run time of mower 2 decreased to an average of 
79 minutes while the run time of the competitive mower decreased to an 
average of 47 minutes. Thus, the run time of mower 2 decreased only 
approximately 30% from its free run time while mulching while the run time 
of the competitive mower 2 decreased approximately 53% while mulching in 
similar conditions. Mower 2 can simply run longer while mulching than a 
similar competitive mower due to the use of wedge-shaped extension 48. 
Wedge-shaped extension 48 is shown as being located at the front of cutting 
chamber 10 and extending forwardly therefrom. This allows the grass 
clippings to be mulched down into the grass in advance of cutting blade 
22. Longer clippings which are not hidden well in the grass will be picked 
up again when the blade passes over them and recut, further enhancing the 
mulching effectiveness of mower 2. 
However, much of the decrease in power consumption exhibited by use of 
wedge-shaped extension 48 is thought to be due simply to its ability to 
more quickly allow the clippings to exit from the otherwise generally 
closed cutting chamber 10. In this regard, placement of wedge-shaped 
extension 48 towards the front of cutting chamber 10 is not critical. It 
could as well extend rearwardly from the rear of cutting chamber 10. 
Various other modifications of this invention will be apparent to those 
skilled in the art. For example, if an AC motor is placed within motor 
compartment 26, the actual motor 26 can be placed over floor 76 and a belt 
transmission can be used to drive a blade spindle mounted in the 
pie-shaped portion 74 of deck 6. In addition, while use of an electric 
motor 24 in conjunction with wedge-shaped extension 48 of cutting chamber 
10 is particularly effective, a cutting chamber with such an extension 
will also increase the mulching effectiveness of a mower powered by a 
gasoline engine, particularly by such engines having lower power. 
Accordingly, the scope of this invention is to be limited only by appended 
claims.