Note: Descriptions are shown in the official language in which they were submitted.
CA 02490960 2004-12-20
- Attorney Docket No. 319i]-000056
BED KNIFE AND METHOD OF FORMING
FIELD OF THE INVENTION
[0001 ] This invention generally relates to bed knives for reel mowers
and, more particularly, relates to an improved bed knife and method of forming
the same capable of simplifying manufacture and reducing overall manufacturing
costs.
BACKGROUND OF THE INVENTION
[0002] Reel mowers use a scissoring action to shear grass and like
foliage. Such reel mowers are more expensive and require more maintenance
than rotary mowers, however they are preferred by golf courses and the like
where appearance and healthy grass are important. Individual reel mower
assemblies are quite narrow and consequently reel mower units commonly
comprise a plurality of side-by-side reel mower assemblies.
[0003] Examples of such mowers are disclosed in U.S. Pat. Nos.
5,291,724, 5,477,666 and 6,318,059. In a typical reel mower assembly, an
attachment member, commonly called a bed bar, is attached to the apparatus in
rigid relationship to the reel and a replaceable bed knife is attached to the
bed
bar. The reel, bed bar, and bed knife are oriented such that the bed knife is
held
parallel to the reel axis and in close proximity to the reel knives so that a
shearing
action is achieved between the reel knives and the bed knife. Typically, an
adjustment mechanism is provided to allow movement of the bed bar relative to
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Attorney Docket No. 3~ 91 J-000056
the reel so that the bed knrfe can be moved into proper relationship with the
rotating reel knives.
[0004] ConventionaNy, the bed knife is attached to the bed bar with a
plurality of screws placed through holes in the bed knife and engaging
threaded
holes in the bed bar. Typically, ten or more screws are used to insure that
the
bed knife remains flat relative to the bed bar and the reel knives.
Additionally,
these conventional bed knifes are also formed from rqlatively thick steel
stock to
permit the fasteners to be countersunk therein. Suc Ih arrangement permits the
fasteners to be generally flush with the bed knife to prevent or, at least,
minimize
any contact between the fastener head and the turf. The thickness of the bed
knife minimizes deformation caused by tightening the fasteners.
[0005] Changing the bed knife requires that these fasteners be
removed and then replaced. Typically, the bed knife is attached to the
underside
of the bed bar so that the apparatus must be raised sufficiently, or partially
disassembled, to allow access to the underside of the reel mower assembly to
remove the screws and the bed knife. A reel-mower unit, such as is used by a
golf course or the like, may comprise eight or ten individual reel mower
assemblies, and changing bed knives on such a mower unit requires significant
labor time and corresponding downtime.
[0006] Similarly, the fasteners that fix the bed knife to the bed bar such
that when a stone or similar debris enters the mower, it can jam between the
fixed bed knife and the reef, causing damage to one or more portions of the
apparatus. Similarly should the bed knife contact a substantially buried
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obstruction, the bed knife can be damaged as it bounces over the obstruction.
While the bed knife can simply be replaced, damage to the reel is generally
much
more costly and problematic, given the close tolerances required for proper
operation.
SUMMARY OF THE INVENTION
[0007] It is the object of the present invention to provide an improve
reel mower assembly, and an improved bed knife that can be attached to
existing
reel mower assemblies, that allows for quick changing of the bed knife with
significantly reduced labor and is downtime compared to the prior art.
[Q008~ In a first aspect the invention provides a reel mower assembly
comprising a mower reel rotatably mounted to a frame, and a drive operative to
rotate the reel about a reel axis. At least one magnet is mounted on the frame
and a bed knife is magnetically held against the magnet in an operating
position
such that the bed knife is oriented in cutting relationship with the reel.
Engagement means are operative to prevent sliding movement of the bed knife
with respect to the magnet while allowing the bed knife to rnove away from the
magnet when a separating force is exerted on the bed knife in a direction away
from the magnet that is greater than an attractive force exerted on the bed
knife
by the magnet when the bed knife is in the operating position.
[0009] In a second aspect the invention provides an apparatus adapted
for attachment to a reel mower assembly comprising a mower reel rotatably
mounted to a frame and a drive operative to rotate the reel about a reel axis.
The
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Attorney Docket No. 3191 J-000056
l
apparatus comprises a bed bar adapted for attachment to the frame
s~rbstantialty
parallel to the reel axis and a plurality of magnets mounted on the bed bar. A
bed
knife is magnetically held against the magnets in an operating position such
that
tfie bed knife is oriented in cutting relationship with the reel when the bed
bar is
attached to the frame. Engagement means are oRerative to prevent sliding
I.
movement of the bed knife with respect to the magriets while allowing the bed
knife to move away from the magnets when a separating force is exerted on the
bed knife in a direction away from the magnets that isle greater than an
attractive
force exerted on the bed knife by the magnets when the bed knife is in the
operating position.
[0010 The engagement means can comprise protrusions extending
from one of the frame and bed knife into corresponding recesses in the other
of
the frame and bed knife. Alternatively, ridges could be formed on the frame
such
that the ridges bear against the front edge and side edges of the bed knife.
Such
ridges would prevent rearward or sideways movement, leaving the front cutting
edge open and in cutting relationship to the reel. Little forward directed
force will
ordinarily be encountered by the bed knife in such a reel mower assembly, and
such forward force could be resisted by the magnets. The protrusions and
recesses have the advantage of resisting sliding forces forward, rearward or
sideways. Both ridges and protrusions allow a separating force to be exerted
on
the bed knife to overcome the magnetic force holding the bed knife to the
magnets in order to remove the bed knife.
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Attorney Docket No. 3191 J-000056
(0011] in a third aspect the invention provides, in a reel mower
assembly comprising a mower reel rotatably mounted to a frame and a drive
. operative to rotate the reel about a reel axis, a method of holding a bed
knife in
an operating position such that the bed knife is oriented in cutting
relationship
with the reel. The method comprises mounting at least one magnet on the frame,
magnetically holding the bed knife against the magnet in the operating
position,
and preventing sliding movement of the bed knife with respect to the magnet
while allowing the bed knife to move away from the magnet when a separating
force is exerted on the bed knife in a direction away from the magnet that is
greater than an attractive force exerted on the bed knife by the magnet when
the
bed knife is in the operating position.
[0012] Commercial grade magnets are available of sufficient strength
such that when they are built into the supporting frame for the bed knife,
typically
on a frame portion called the bed bar, they will hold the bed knife in the
operating
position resisting considerable separating forces that might be encountered by
the bed knife in operation. The engagement means prevents sliding movement of
the bed knife with respect to the bed bar in response to the rearward force of
the
reel pulling grass against the forward edge of the bed knife, or in response
to
sideways forces during turns. The engagement means aligns the bed knife in the
proper operating position When the bed knife and bed bar are clean, the bed
knife can be readily maneuvered into engagement with the protrusions, ridges
or
the like and will then snap into place in response to the force of the
magnets.
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Attorney Docket No. 3 ~ 91 J-000056
[0013] The magnetic attachment of the bed knife to the ~ tame has
numerous advantages over the mechanical or screw attachment of the prior art.
The magnetic attachment results in a quick change assembry where the bed
knife can basically be changed by prying it away from the magnets and
attaching
another bed knife to the magnets inits place without t j a need to disassemble
the
reel mower assembly from the remainder of the reel mower unit to access the
screws holding the bed knife in place.
[0014) The present invention yields a relatively "tool-less" bed kn'rfe
changing operation. The only tool required to remove a bed knife from the
frame
would be a blade or the like to pry the items apart. The strength of the
magnets
and number of magnets used in the frame to hold the bed knife in place could
be
adjusted or varied depending on the circumstances.
[0015) The magnetic attachment also reduces maintenance costs by
allowing the bed knife to be pulled away from its magnetic attachment and
released from the bed bar when an obstruction such as a rock or the like is
encountered. Damage to the reel and bed knife is thereby reduced.
[0016) While permanent magnets will likely be most widely suited,
electromagnets could also be used to hold the bed knife in place. Where
electromagnets are used, it would be even easier to release the blade from the
frame, since by deactivation of the electromagnets the blades could easily be
removed therefrom.
[0017] In addition to manufacturing a completed new reel apparatus in
accordance with the present invention, a retrofit bed bar and bed knife could
also
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CA 02490960 2004-12-20
Attorney Docket No. 3191J~000056
be designed in accordance with the present invenron to be retrofitted onto
various existing reel mower units.
[OOi8j Still further it is an object of the present invention to provided a
method of manufacturing a bed knife for a reel mower. The method includes cold
roll forming spring steel, flattening and straightening the spring steel,
shaping the
spring steel through a plurality of rollers to impart a bending force upon the
spring
steel to define a mounting portion and an upturned portion, and grinding a
portion
of the upturned portion to form a cutting 'edge.
[0019] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter. It should
be
understood that the detailed description and specific examples, while
indicating
the preferred embodiment of the invention, are intended for purposes of
illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention will become more fully understood from
the detailed description and the accompanying drawings, wherein:
[0021] FIG. 1 is an exploded perspective view showing a reel mower
assembly and typical bed knife mounting assembly of the prior art;
[0022] FIG. 2 is a schematic side view showing the reef and bed kn'rfe
mounting arrangement of the prior art reef mower assembly of FIG. t;
[0023] FIG. 3 is a perspective view of the top of a magnetic bed bar of
one embodiment of the present invention;
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Attorney Docket No. 3~91J-OOOO56
[0024] FiG. 4 is a is a perspective view of the bottom of they bed bar of
FIG. 3;
[0025] FIG. 5 is a perspective view of a bed knife for attachment to the
magnetic bed bar of FIG. 3;
[0026] FIG. 6 is a schematic side view of the bed knife of FIG. 5 in the
operating position on the magnetic bed bar of FIG. 3. i
[0027] FIG. 7 is a schematic side view of ~a, n alternate bed knife and
magnetic bed bar;
[0028] FIG. 8 is a side view of the bed bar of FIG. 7 contacting an
obstruction and indicating the forces exerted on the bed knife to release it
from
the bed bar;
[0029] FIG. 9 is a plan view of a bed knife according to a first method
of manufacture;
[0030] FIG. 10 is a cross sectional view of the bed knife of FIG. 9;
[0031 j FIG. 11 is a plan view of the blank used in forming the bed knife
of FIG. 9;
[0032) FIG. 12 is a plan view of the bed knife of FIG. 9 following
multiple grinding operations;
[0033] FIG. 13 is a cross sectional view of the bed knife of FIG. 12;
[0034] FIG. 14 is a plan view of the bed knife of FIG. 12 following the
final grinding operation;
[0035) FIG. 15 is a cross sectional view of the bed knife of FIG. 14;
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(0036] FIG. 16 is a plan view of a bed knife according to a second
method of manufacture; and
[0037] FIG. 17 is a cross sectional view of the bed knife of FIG. 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(0038] The following description of the preferred embodiments is
merely exemplary in nature and is in no way intended to limit the invention,
its
application, or uses.
[0039] FIG. 1 schematically illustrates the major parts of a prior art reel
mower assembly comprising a mower reel 2 rotatably mounted to a frame 4. A
drive, not shown, is operative to rotate reel 2 about a reef axis RA. A bed
bar 6
forms a portion of frame 4, and bed knife 8 is attached to bed bar 6 by screws
10.
Typically, some adjustment mechanism, not shown, is provided to vary the
position of bed bar 6 with respect to reel 2 so that the proper cutting
relationship
between bed knife 8 and reel 2 may be achieved. FIG. 2 illustrates
schematically
the orientation of reel 2, bed bar 6, and bed knife 8 of the prior art.
[0040] FIGS. 3 and 4 illustrate an embodiment of a magnetic bed bar
16 of the invention. The illustrated bed bar 16 is configured to attach to
frame 4
of the prior art reel mower assembly of FIG. 1 in the same manner as the prior
art
bed bar 6, so that magnetic bed bar 16 can be retro-fit to existing reel mower
assemblies. The bed bar frame portion configuration is fairly widespread in
various brands of existing reel mower assemblies, allowing for relatively
simple
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modification of the magnetic bed bar such that it may be substitute d for the
existing bed bars.
[0041 ] As illustrated in FIGS. 3 and 4, a plurality of magnets 20 are
mounted in a spaced apart relationship on bed bar 16, and in the illustrated
embodiment magnets 20 are embedded in bed bar 16 such that a lower face 21
thereof is substantially flush with bottom surface 22 of magnetic bed bar 16.
[0042] Bed knife 18, illustrated in FIG. 5, is' magnetically held against
magnets 20 in an operating position as illustrated in FIU~. 6 such that bed
knife 18
is oriented in cutting relationship with reel 2 in the same fashion as bed
knife 8 of
the prior art illustrated in FIG. 2.
[0043] Engagement means are operative to prevent sliding movement
of bed knife 18 with respect to magnets 20. In the illustrated embodiment the
engagement means comprises a plurality of protrusions, illustrated as pegs 26,
extending from bed bar 16 into a corresponding recess, illustrated as a hole
28,
in bed knife 18. Conversely as illustrated in FIG. 7, pegs 32 could extend up
from
bed knife 18A into corresponding holes 34 in bed knife 16A. Further engagement
means are illustrated in FIG. 6 as a ridge 30 bearing against opposite end
edges
18A and rear edge 18B of bed knife 18.
[0044] While preventing sliding movement, the engagement means,
illustrated as pegs 26 in holes 28, and as ridge 30, but also including other
means, also allows bed knife 18 to move away from magnets 20 when a
separating force is exerted on bed knife 18 in a direction away from magnets
20
that is greater than an attractive force exerted on bed knife 18 by magnets 20
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Attorney Docket No. 3191J-000056
when bed knife 18 is in the operating position. While allowing bed knife 18 to
be
easily removed by prying it away from bed bar 16, this configuration also
allows
bed knife 18 to release from bed bar 16 when an obstruction is encountered.
[0045] FIG. 8 illustrates schematically contact of bed knife 18 moving in
direction T with a typical obstruction ill as a partially buried stone 40. The
contact
causes a force F to be exerted on bed knife 18. The major component of this
force F is exerted rearward, as illustrated by the arrow FR, however there is
also
a smaller component FD exerted downward such that bed knife 18 is pushed
away from bed bar 16 and magnets 20. When this component of force FD
exceeds the magnetic attractive force of magnets 20, bed knife 18 will release
from bed bar 16. In the prior art bed knife attached by screws, more damage
would- occur, since the bed knife would have to ride over the obstruction.
Similarly where a stone or the like comes between the reel and the bed knife,
a
like force is exerted which can release the bed knffe, reducing the
possibility of
severe damage to the reel which can be costly to repair.
[0046] Ridge 30 alone could provide satisfactory operation with a new
bed knife 18, as it essentially forms a low pocket that closely Sts edges 18A,
18B
of bed knife 18. Sideways and rearward sliding movement with respect to
magnets 20 is thus prevented. It is however possible to make bed knife 18
double edged such that the front and rear edges 18C, 181 B are both cutting
edges. holes 28 and pegs 26 are oriented such that bed knife 18 can be rotated
bringing rear cutting edge 18t3 to the front, thereby doubting the life of bed
knife
18. With such a double-edged bed knife 18, the front edge becomes worn and
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Attorney Docket No. 3~91J-000056
rounded during use such that the ridge bears against a rounded eda~e that may
slide over the ridge when rearward forces arc applied. The pegs and holes are
not affected by wear on the bed knife-edges and will maintain the bed knife in
position when it is rotated. The use of ridge 30 in combination with pegs 26
and
holes 28 helps to align the bed knife with the pegs during installation.
[0047) The present invention could be practiced in a number of
fashions including by manufacturing new reel cutting~assemblies in accordance
with the present invention, or alternatively, by producing a retrofit bed bar
or
support frame kit which would allow the magnetic blade attachment of the
present invention to be implemented on an existing mower.
[0048 Additionally, magnetic bed knife 18 of the present invention
could be manufactured according to various manufacturing processes. More
particularly, as seen in F1GS. 9-15, bed knife 18 may be made of carbon steel,
specifically AISI 1566 Hot Rolled Pickled and Oiled steel, which is generally
referenced at numeral 100. Carbon steel bed knife 100, like bed knife 18, is
adapted to be magnetically held against magnets 20 in an operating position on
bed bar 16 as illustrated in FIG. 6 such that bed knife 100 is oriented in
cutting
relationship with reel 2 in the same fashion as bed knife 18.
[0049) With particular reference to FIGS. 9-15, the manufacturing steps
of carbon steel bed knife 100 will now be discussed in detail. A generally
planar
blank 101 is first cut to length. Planar blank 101 is then fed through a
stamping
or pressing machine that first flattens and straightens planar blank 101 and
then
imparts a bending force upon the blank. Although this shape can vary among
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CA 02490960 2004-12-20
Attomdy Docket No. 3191 J-000056
reel mowers, the present shape of bed knife 100 includes a generally planar
mounting portion 102 and an upturned cutting portion 104. As best seen in FIG.
10, upturned cutting portion 104 initially includes a radius portion 106
interconnecting a distal end i 08 with mounting portion 102. Specifically, as
a
result . of the stamping process used to form carbon steel, radius portion 106
includes an outer surface 1 i 0 that, as seen in FIG. 10, extends below a
lower
surface 112 of mounting portion i 02. As should be appreciated by one skilled
in
the art, this condition of outer surface 110 extending below lower surface 112
iS
undesirable as it may impede proper turf cutting and/or may contact the ground
surface. Furthermore, this condition may further limit the reel mower's
minimum
cutting height. Accordingly, it is preferable to grind off this outer surface
110 to
define a genArally unobstructed lower surface.
(0050] As best seen in FIGS. 12 and 13, bed knife 100 is illustrated
following completion of a series of grinding operations sufficient to remove
outer
surface 110 and define a plurality of faces to create a final desired shape.
Specifically, as seen in FIG. 13, bed kn'rfe 100 includes a tournament cut
face
114 extending upwardly from lower surtace ~ 112 of mounting portion 102.
Preferably, tournament cut face 114 extends upwardly from lower surface 112 at
a relative angle of about 5 degrees. Tournament cut face 114 transitions into
a
super tournament cut face 116 that extends further upwardly at a greater
inclination of about 8 degrees relative to lower surface 112. Bed knife 100
includes a front face 118, which is at about 90 degrees relative to lower
surface
112, and a top face 120, which is at about 8 to 10 degrees relative to lower
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t
Attorney Docket No. 3 91J-000056
surface 112. Front face 118 and top face 120 intersecting at an Ledge 121.
Tournament cut face 1 i 4, super tournament cut face 116, front face 118, and
top
face 120 are each formed through various grinding operations that requires bed
knife 100 to be fed through a milling machine. Following these grinding
operations, bed knife 100 is then heat-treated to pr ivide sufficient hardness
to
i
reduce the wear of bed knife 100 during operation.
[0051] Referring now to FIG. 12, following i heat treatment, bed knife
100 further includes a pair of apertures 122 formed through mounting portion
102. This pair of apertures 122 is used during manufacturing to position bed
knife 100 during subsequent grinding operations. Additionally, a second pair
of
apertures 124 is formed through mounting portion 102. This second pair of
apertures 124 is sized, similar to holes 28, to receive pegs 26 of bed bar 16.
[0052] Finally, as seen in FIGS. 14 and 15, a final grind of bed knife
100 is completed. Specifically, through a subsequent grinding operation,
following heat treatment, top face 120 is finish ground down such that it is
about
5.5 degrees inclined relative to lower surface 112. Similarly, front face 118
is
ground down to create a cutting edge 126 in place of edge 121. The particular
inclination of cutting edge 126 is dependent upon the desired cutting
configuration relative to reel 2.
(0053] Although bed knife 100 provides a number of beneficial cutting
properties and prolonged wear, the manufacturing thereof may lead to
undesirably high costs and complexity. Therefore, a second embodiment of the
present invention provides a preferred method of manufacturing the bed knife
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Attorney Docket No. 3191J-000056
which is capable of eliminating many of the grinding steps, heat treatment,
and
complexity of construction.
[0054] With particular reference to FIGS. 16 and 17, a bed knife 200 is
illustrated being manufactured from a simplified process. More particularly,
bed
knife 200 fs made of spring steel, specifically C1095 Scaleless Blue-Tempered
Spring Steel, ASTM A682, which is hardened to a minimum Rockwell number of
about 47C. Spring steel bed knife 200, like bed knifes 18 and 100, is adapted
to
be magnetically held against magnets 20 in an operating position on bed bar 16
as illustrated in FIG. 6 such that bed knife 200 is oriented in cutting
relationship
with reel 2 in the same fashion as bed knife 18.
[0055] Still referring to FIGS. 16 and 17, the manufacturing steps of
spring steel bed knife 200 will now be discussed in detail. As will be
appreciated,
the manufacturing steps of spring steel bed knife 200 are dramatically
simplified
relative to bed knife 100, thereby leading to reduced manufacturing complexity
and cost. A generally planar blank (not shown) is fed into a cold roll-forming
machine that imparts a bending force upon the blank. Preferably, the planar
blank is a roll of spring steel that can quickly and easily be shaped in a
continuous, uninterrupted process. As best seen in FIGS. 16 and 17, the blank
is
shaped through a series of rollers into a desired shape. Due to the nature of
spring steel, this shaping process may require one or more bending and over
bending operations to produce the desired final shape.
[0056j Although the final shape can vary among reel mower designs,
the present shape of bed knife 200 includes a generally planar mounting
portion
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Attorney Docket No. 3y~91J-000056
202 and an upturned cutting portion 204. As best seen in FIG. 1T, upturned
cutting portion 204 extends upwardly from mounting portion 202 at a relative
angle of about 9 degrees. As can be appreciated from the figures, unlike bed
knife i 00 that includes downwardly protruding outer surface 110 of radius
portion
106 caused during the stamping process, the cold ~ II forming process of the
present embodiment does not create such effect, thereby eliminating the need
to
i
grind tournament cut face 114 and super tournament cut face 116. Therefore,
the use of spring steel permits the use of roll forming rather than stamping,
which
eliminates a number of grinding operations, but for a final grind of front
face 218
to define a cutting surface.
[0057] As seen in FIG. 16, bed knife 200 further includes a pair of
apertures 224 are formed through mounting portion 202. This pair of apertures
224 is sized, similar to holes 28, to receive pegs 26 of bed bar 16.
[0058) Spring steel bed knife 200 provides a number of advantages
over conventional screw-on bed knives and, even, bed knife 100. Specifically,
bed knffe 200, being made of spring steel, enables it to be made according to
a
simple cold roll forming technique. This technique, which has not been used
before to form magnetic bed knives, dramatically simplifies the manufacturing
process, thereby eliminating the need for complex flattening, straightening,
forming, grinding, and heat-treating operations.
[0059] The description of the invention is merely exemplary in nature
and, thus, variations that do not depart from the gist of the invention are
intended
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to be within the scope of the invention. Such variations are not to be
regarded as
a departure from the spirit and scope of the invention.
17
