Note: Descriptions are shown in the official language in which they were submitted.
CLUTCH AND BRAKE MECHANISM
Field To Which Invention Relates
1 My invention relates to a clutch and brake mechanism
particularly for the concurrent braking and declutching of a
rotatable working element and for the concurrent unbraking and
clutching of the working element. It is especially suitable
for a rotary-type lawn mower so that the working element, the
rotating blade, is braked against rotation at substantially
the same time that the blade is declutched from the driving shaft
of the mower motor and so that the blade is clutched to rotate
with the shaft at substantially the same time that the blade
is unbraked and permitted to rotate.
Background Art Of The Invention
The related background art known to the Applicant but
which does not teach, disclose, or suggest the present invention,
includes the following United States patents:
No. 3,871,159 - Charles R. Shriver
No. 4,035,994 - Stephen J. Hoff
No. 4,141,439 - James M. Lunde et al
No. 4,148,173 - Stephen J. Hoff
No. 4,205,509 - Takeshi Miyazawa et al
Statement Of The Invention
It is an object of the invention to provide an improved
clutch and brake mechanism of relatively simple and economic
construction which provides for quick and efficient substantially
concurrent braking and declutching of a rotatable working element,
such as the blade of a rotating type lawn mower, and the substan-
tially concurrent unbraking and clutching of the rotatable work-
in~ element.
It is a further object to assure that the motor-driven
rotatable working element, such as the blade of a rotating type
lawn mower, does not continue to rotate for any appreciable length
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1 of time after the working element is declutched and no longer
being motor-driven.
Another object is to improve safety in the use of machines
having rotatable working elements such as rotating type lawn
mowers having blades driven by the mower motor.
A further object is to facilitate the control of the
rotation of a motor-driven rotatable working element, such as the
blade of a rotary type lawn mower, by use of a "dead-man" con-
trol, by assuring that the rotation of the rotatable working
element by the still operating motor stops very quickly after
the "dead-man" control i5 released.
Another object is to provide more responsive control of
the rotation of a rotatable working element, such as the blade of
a rotary type lawn mower, to assure that upon declutching of the
working element from a driving motor, the rotation of the work-
ing element is almost simultaneously braked to discontinue
rotation, and also to assure that upon clutching of the working
element to the driving motor, the working element is not braked
but is free to rotate.
Other objects and advantages may be observed from the
following description of the invention in conjunction with the
several drawings in which:
Figure 1 is a longitudinal sectional view taken through
the improved clutch and brake mechanism and illustrating the
parts in braked and declutched positions;
Figure 2 is a partial sectional view showing a portion
of the view in Figure 1 but illustrating the parts in unbraked
and clutched positions;
Figure 3 is a plan view, partially in section, of the
annular rotatable member apart from the mechanism shown in the
view of Figure 1 and which carries the friction elements of the
clutch and brake mechanism;
1 ~ 7~ 9
1 Figure 4 is a longitudinal sectional view taken through
the lines 4-4 of Figure 3;
Figure 5 is a plan view of the fan apart from the mech-
anism shown in the view of Figure l;
Figure 6 is a cross-sectional view through a blade of the
fan and is taken through the line 6-6 of Figure 5;
Figure 7 is a longitudinal sectional view of the fan
shown in Figure 5 taken in a plane passing through the axis
of the fan;
Figure 8 is a plan view, partially in section, of the
brake plate in the mechanism showing the rotative position of
the brake plate in the cup member or housing extension when
the parts are in the braked and de-clutched positions;
Figure 9 is a plan view somewhat similar to that of
Figure 8 but showing the rotative position of the brake plate
when the parts are in the unbraked and clutched positions; and
Figure 10 is a side view of the brake plate removed from
the mechanism shown in Figure 1.
The present invention is here described in connection with
its use in a rotary type lawn mower having a motor driven rotat-
able blade for which it is especially adapted, although it is
also useful in connection with other machines having a motor
driven rotatable working element. The best and preferred
embodiment of the invention as presently known to the inventor
is as herein disclosed.
The lawn mower to which the invention is here applied
has a motor or engine 11, which may be an internal combustion
type motor or an electric motor, which is mounted on a mower
housing 12. A fragmentary portion of the housing 12 and motor
11 is shown in Figure 1. The housing 12 has a downwardly ex-
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1 tending cylindrical portion forming a cup member 13 on the
under portion of the housing 12 proper. The cup member 13 may
be bolted, welded or otherwise secured to the housing 12 proper.
The motor 11 has a vertically extending shaft extending
downwardly therefrom and in the usual manner the motor 11 drives
the shaft 14 to rotate therewith.
Secured to the shaft 14, and splined thereto so as to
rotate with the shaft, is a fan 15. This fan 15 is best shown
in Figures 5, 6 and 7 as removed from the mechanism to be shown
alone. The fan 15 has a rim 15B joined by multiple spaced fan
blades to a central hub 15A. The hub 15A is splined to the
shaft 14 to cause rotation of the fan with the shaft. The
different fan blades are oriented in respect to the direction of
the rotation of the fan so as to blow or impel air downwardly
about the mechanism within the cup member 13 for the purpose of
blowing and expelling debris, such as particles of cut grass,
oil and foreign material outwardly and away from the mechanism.
Mounted to the fan hub 15A concentrically of the shaft 14
is a steel clutch plate 16 by means of bolts 17. This clutch
plate 16 as illustrated is in the form of an inverted saucer
having its mouth directed downwardly. A central opening in the
clutch plate 16 accommodates the hub 15A. The clutch plate
rotates with the hub 15A and with the shaft 14 to which it is
splined, and therefore the clutch plate 16 is rotatively driven
by the motor 11.
The outer peripheral border of the clutch plate 16 is
inclined downwardly at an approximate angle of 45 to the gen-
eral plane of the clutch plate 16, which plane is normal to the
axis of the shaft 14. This outer peripheral border provides on
its under surface the inclined annular clutching surface 16A
l~t-'~ 9
1 disposed as shown.
Rotatably mounted on the lower free end of shaft 14 is
a rotatable plate member 18 having the configuration illustrated
in Figures 1, 2, 3 and 4. This rotatable plate member 18 has
upturned an outer flange portion 18A as illustrated and has the
ribs and bosses pressed therein in the configuration shown. A
central cylindrical portion 18C of the member 18 accommodates
a bearing assembly 23 which is interposed between the lower end
of hub 15A and the walls of cylindrical portion 18C. The rotata-
ble plate member 18 is mounted on the hub 15A through the bearingassembly 23 in such manner that the shaft 14 may rotate free of
the rotatable plate member 18 even when the plate member is
braked and thus restrained against rotation.
A cutting blade 20 of usual form used in a rotary type
lawn mower is bolted by bolts 22 and nuts 22A. This blade 20
is the rotatable working element on this machine known as a lawn
mower. A spacer washer 19 is interposed between the blade 20
and the rotatable plate member 18. The arrangement is such
that the rotatable plate member 18, washer 19, and blade 20 are
joined as a unit and either rotate in unison with the shaft 14
or remain stationary or non-rotative together even while the shaft
14 and fan 15 may be rotating by the driving force of the motor
17.
A bolt 21 threadably secured to shaft 14 and fan hub
15A, together with a washer member 21A, extend through central
openings in blade 20 and in spacer washer 19 to secure the inner
race of bearing assembly 23 to the hub 15A.
Pivotally mounted by means of three pivot pins 25, re-
spectively, to the rotatable plate member 18 are three steel
carrier members having the angular configuration, as seen in
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1 the plan view of Figure 3. Each of these three carrier members
24 has a finger portion 24A extending from the side of the outer
free end of the respective carrier members 24 as better seen
in the drawings.
Three compression springs 26 are mounted on the finger
portions 24A, respectively, and extend radially inward to en-
gage the central cylindrical portion 18C of the rotatable plate
member 18. Small bosses 18B on the cylindrical portion 18C
and equidistantly spaced around the cylindrical portion 18C
accommodate the inward ends of springs 26 and thus maintain the
springs in position. The bias of the springs 26 is such as to
resiliently urge the carrier members 24 to swing on their re-
spective pivot pins 25 radially outward.
Mounted on each of the carrier members 24 adjacent the
outer free ends of each are friction elements 27. These fric-
tion elements are composed of molded plastic brake material
variously composed of different compositions of resin, asbestos,
lignin derivitives, powdered metal and other known brake mate-
rial having appropriate friction and wear characteristics.
Each of these three friction elements has at its outward
peripheral portion an inclined braking surface 27A of arcuate
form and disposed at substantially a 45 angle to the plane of
rotatable plate 18 which is normal to the axis of shaft 14.
Also each of these friction elements 27 spaced radially
inward and on a higher level, as seen in the drawings, has an
inclined clutching surface 27B disposed at substantially a 45
angle to the plane of rotatable plate member 18 which is normal
to the axis of shaft 14. The inclination of clutching surface
27B is such as to substantially complement the inclined surface
16A of clutch plate 16 so that they may closely engage along
1 the length of clutching surface 27B.
An annular brake plate 28 is disposed concentrically of
the hub lSA and shaft 14. The brake plate 28 has a cylindrical
portion 28A and an inturned flange portion 28D about its upper
end. The cylindrical portion 28A has equidistantly spaced
therearound three helically disposed grooves 28B formed in the
wall thereof in the manner illustrated in Figures 8, 9 and 10.
Vertically directed ducts or openings 28A extend downwardly in
the wall to provide ingress into the respective grooves 28B.
At the bottom or lower free end of the brake plate the plate i3
flared outwardly to provide the inclined braking surface 28C
on its underneath or interior surface. This braking surface
28C is inclined at approximately a 45 angle to the transverse
plane of the mechanism, which plane is normal to the axis of
shaft 14. The inclination of braking surface 28C complements
the inclined braking surfaces 27A of the friction elements 27
so that they may closely engage along the length of braking
surface 27A.
Carried by three nylon socket members 30 equidistantly
spaced apart mounted on anchoring brackets 31 formed radially
inward of cup member 13, are three steel balls 29 which protrude
from nylon socket members 30 radially inward to the cylindrical
portion 28A of the brake plate 28. The balls 29 interfit with
the helical grooves 28B so as to ride along the incline of the
helical grooves 28B. The balls 29 may be introduced into the
grooves 28B through the ducts 28E upon longitudinal movement of
brake plate 28 relative to the cup member 13 carrying the balls
29.
A screw reaction is provided by the balls 29 in the
grooves 28B whereby a rotational movement of the brake plate 28
1 is translated into a longitudinal movement of the brake plate
28 relative to the cup member 13 and housing 12. Thus, rotation
of brake plate 28 is translated into an up or down longitudinal
movement of the brake plate parallel to the axis of shaft 14,
the direction of the longitudinal movement up or down being
dependent on the direction of the rotational movement imparted
to the brake plate.
Tending to impart a rotational movement to the brake
plate 28 so as to be translated into a longitudinal movement
which acts to lower the brake plate downwardly such as to the
position shown in Figure 1, are three extension springs 32.
Each of these equidistantly spaced springs 32 have one end an-
chored to anchoring brackets 31 on cup member 13 by hooked por-
tions 32B secured to the respective brackets 31. Each of these
springs 32 have their opposite end anchored by hooked portions
32A to the brake plate 28. The bias of these extension springs
32 is such as to impart a rotational movement to the brake plate
28 so as to move to the position shown in Figure 8, wherein the
brake plate 28 is shown in braking position shown in Figure 1.
For OVerCQming or opposing the resilient bias of springs
32 and thus to permit the parts to be in the unbraked positions
shown in Figures 2 and 9, a cable 34 is secured by an anchoring
pin 33 to the inturned flange portion 28D of brake plate 28.
This cable 34 extends through a fair lead 35 in one of the nylon
blocks 30 from where it extends through a sheath or tubular
casing 36 to a location externally of the housing 12 and cup
member 13. A common use of the improved clutch and brake mech-
anism is its use in conjunction with a "dead-man" control. For
diagrammatically illustrating this use, there is shown, in Fig-
ures 8 and 9, the cable externally of the housing in the form
1 of a broken line which is connected to a "dead-man" control
lever 37 swingably mounted on a supporting structure 38.
Typically in a lawn mower use of the invention, the supporting
structure 38 is a handle of the mower held by the operator of
the mower, and the lever 37 is pivotally mounted on th~-handle
in position to be simultaneously held and pressed against the
handle 38 by the operator. Upon release of the "dead-man" con-
trol lever 37 by the operator, the force of springs 32 takes
over as there is no longer tension on cable 34 and the bra~e
plate moves rotationally from its non-braking position shown
in Figure 9 to its braking position shown in Figure 8.
Thus, the movement of the brake plate 28 is between the
braking position of Figure 1 to the non-braking position of
Figure 2.
It is to be noted that the radial spacing between inclined
braking surface 27A and the inclined clutching surface 27B is
such that when the braking surface 27A is engaged by inclined
surface 28C of the brake plate 28, the engaged friction element
27 is swung on its respective carrier member 24, in opposition
to its respective spring 26, radially inward sufficiently that
inclined clutching surface 27B is moved away from, and out of
clutching engagement with inclined clutching surface 16A of
clutch plate 16.
Upon the raising of the brake plate 28, by translating
rotational movement thereof to longitudinal movement, from its
position shown in Figure 1 to its position shown in Figure 2,
the friction elements 27 swing out under the urging of springs
26 to their positions shown in Figure 2 where the inclined
clutching surfaces 27B of the friction elements 27 clutchingly
engage the inclined surface 16A of clutch plate 16.
1 Thus, by this mechanism there is assurance that upon the
declutching action, the braking action almost immediately occurs
so that any rotation of the blade 20 thereupon and quickly ceases.
This assures safety in the use of the lawn mower or other machine
having a motor-driven rotatable working element. Also, upon the
unbraking operation the clutching action almost immediately
occurs and the mower or other machine may be operated. The
"dead-man" control is particularly adapted for use in controlling
the mechanism here disclosed and utilizing its advantages.
It may be noted that by the arrangement shown and
described the braking action tends to be self-energizing.
After the brake plate and braking surfaces of the friction
elements initially engage, the frictional drag or pull tends
to cause the frictional eelements, mounted by the rivets 39 on
carrier members 24, to shift outwardly to fuller and more com-
plete braking engagement with the brake plate. The brake
plate force directed toward the friction element also increases
because of the reinforcement of the screw action of the brake
plate. Similarly, there is a self-energizing action provided
in the clutching action when the brake plate is raised out of
braking position, in that initial clutching engagement of the
frictional elements with clutching surface of the clutch plate
tends to cause the frictional elements to shift to fuller and
complete clutching engagement with the clutch plate. This
self-energizing of the clutching action is introduced by centrif-
ugal force imparted on the friction elements.
While I have illustrated and described a preferred embodi-
ment of my invention, it will be understood that this embodiment
is by way of example only and not to be construed as limiting.
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