Clutch-brake assembly for rotary implements

The blades of a rotary lawn mower are driven by a constantly rotating shaft through a clutch-brake assembly which, when the operator leaves the operating station of the mower such as the mower handles, automatically disengages the blades from the shaft and brakes the blades while permitting the shaft to continue to rotate. The clutch-brake assembly is self-energizing and normally is engaged but is held in the disengaged condition by an actuator which also is self-energized and which initially is energized by a spring. The latter is effective to disengage the clutch and actuate the brake thereby to prevent the blades from rotating until the operator moves a manual member at the operating station to overcome the spring which initially energizes the actuator. This de-energizes the actuator so that the brake is disengaged and the clutch is engaged whereby the shaft rotates the blades.

BACKGROUND OF THE INVENTION 
Rotary implements such as rotary lawn mowers normally are driven by a motor 
or an engine which drives a shaft coupled to the blades. In usual prior 
constructions, the shaft has driven the blades directly with the result 
that, when the operator leaves the operating station such as the mower 
handles, the blades continue to rotate and this creates a potentially 
hazardous condition. 
SUMMARY OF THE INVENTION 
The general object of the invention is to provide a novel clutch assembly 
which may be interposed between the drive shaft and the rotary implement, 
which automatically disconnects the implement from the drive shaft when 
the operator leaves the operating station and which is comparatively easy 
to use and inexpensive to manufacture. 
A further object is to incorporate a brake in the assembly whereby the 
brake automatically stops the rotation of the implement when the clutch 
disconnects the latter from the drive shaft. 
A more detailed object is to utilize a self-energizing clutch which is 
normally disengaged but is engaged by a relatively low force exerted by 
the operator at the operating station. 
Still a further object is to incorporate a self-energizing actuator which 
normally is urged by a resilient means in the energizing direction to 
disengage the clutch and which is deenergized by the manual means, which 
overcomes the resilient means, to initiate the self-energizing of the 
clutch thereby to couple the drive shaft and the rotary implement by the 
application of a comparatively light force of the operator at the 
operating station. 
It also is an object of the invention to arrange the actuator so that, when 
the actuator is self-energized by the resilient means, the actuator not 
only disengages the clutch but also causes the brake to stop rotation of 
the rotary implement until the operator actuates the manual means. 
The invention also resides in the particular constructions of the clutch, 
the actuator, the brake and the coaction of these elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in the drawings for purposes of illustration, the present 
invention is embodied in a clutch-brake assembly 10 adapted selectively to 
couple or disengage a normally rotating shaft 11 and a rotary implement 
such as the blades 12, which may be formed as a unitary piece, of a rotary 
lawn mower. The shaft is driven by a motor or engine (not shown) and, in a 
manner to be described, the assembly is supported on the frame of the 
mower, a portion 13 of the frame being shown in the drawings. When the 
clutch portion of the assembly 10 is engaged, the shaft 11 drives the 
blades 12 and, when the clutch portion is disengaged, the brake portion 14 
of the assembly becomes operative to stop rotation of the blades while the 
shaft 11 continues to rotate. 
For purposes of both convenience and safety, it is desirable that, when the 
operator of the mower leaves the operating station of the lawn mower such 
as the handles (not shown) of the mower, the motor or engine of the mower 
continues to rotate the shaft 11 but the shaft automatically is disengaged 
from the blades 12 and, preferably, also that the latter are braked 
quickly to a stop. Accordingly, the present invention contemplates an 
assembly incorporating a normally-engaged, self-energizing clutch 15 to 
couple the shaft 11 and the implement 12 and a self-energizing actuator 16 
which is normally energized by a resilient means 17 to hold the clutch in 
the disengaged condition. Means 18 manually operable from the operating 
station overcomes the resilient means to deenergize the actuator 16 and 
permit the clutch 15 to energize and couple the shaft 11 and the implement 
12. As another significant aspect, the invention also contemplates a brake 
portion 14 being incorporated in the assembly 10 and arranged to stop the 
implement when the resilient means 17 energizes the actuator 16 to 
disengage the clutch 15 and with the brake portion being automatically 
disengaged as an incident to the manual engagement of the clutch. As used 
herein, the term "self-energization" has the same meaning as commonly 
understood in the clutch and brake art, that is, with a load applied to 
one of the two elements of the clutch or brake, an actuating force, 
usually comparatively small, is applied to initiate coupling of the two 
elements. Thereafter, the frictional force of the clutch or brake augments 
the actuating force whereby a lesser actuating force is required for a 
given clutch or brake torque. 
In the present instance, the blades 12, which herein constitute the rotary 
implement, are secured to a lower cam member 19 which is engaged by a 
resilient member 20 and the latter urges an upper cam member 21 upwardly 
to bring a friction surface 22 on the upper cam member into engagement 
with an opposing surface 23 on a member 24 fixed to the shaft 11, the 
member 24 and the upper cam member 21 constituting the principal elements 
of the clutch 15. The lower and upper cam members 19 and 21 include one or 
more pairs, herein three, of opposed inclined cam surfaces or ramps 25 and 
26 (FIGS. 7 and 8) formed respectively on the cam members 19 and 21 and 
engage each other (FIG. 7 shows the surfaces separated for clarity of 
illustration). As the upper cam member 21 is begun to be turned by the 
member 24, the cam surface 26 rides up the cam surface 25 and thus the cam 
surfaces produce the self-energizing effect of moving the cam members 
apart and the clutch surfaces 22 and 23 into engagement to couple the 
shaft 11 and the blades 12 with a force which progressively increases 
beyond the force of the resilient element 20. 
Preferably, the clutch member 24 is annular and coaxial with the shaft 11 
with an intermediate cylindrical portion 24a encircling the shaft and 
fixed to the latter by a key 24b. An annular flange 27 integral with the 
upper end of the cylindrical portion 24a provides on its under side the 
friction surface 23 which opposes the surface 21 and is one of the 
engaging surfaces of the clutch 15. At the lower end of the cylindrical 
portion 24a, the clutch member 15 includes an annular section 28 
projecting inwardly under the end of the shaft 11 and a downwardly 
projecting cylinder 29. The lower cam member 19 is journaled on the 
cylinder 19 by a bearing 30 which is held in place by a bolt 31 which 
projects through a collar 32 and the cylinder 29 and is threaded into the 
lower end of the shaft 11, the bearing 30 thereby being clamped between an 
annular shoulder 32a on the collar 32 and the section 28. A flanged cap 33 
covers the bolt 31 and the collar 32 and, as will appear later, is clamped 
against the lower end of the bearing 30 to protect the bearing and other 
moving parts of the entire assembly from dirt and the like. 
The lower cam member 19 is an annulus concentric with the shaft 11 and, as 
stated above, is journaled on the bearing 30 for selective rotation 
relative to the shaft. The blades 12 are fastened to the underside of the 
lower cam member by bolts 34 projecting through holes 35 in the blades and 
threaded into the lower cam member so that the blades rotate with the 
lower cam member and, at the same time, hold the cap 33 in place. With 
particular reference to FIG. 6, the lower cam member is formed with an 
upwardly facing annular surface 36 surrounding the bore 37 which encircles 
the bearing 30 and three teeth 38 project upwardly from the annular 
surface 36 around the bore 37. Each of the teeth 38 provides one of the 
cam surfaces 25 which is inclined upwardly, preferably at an angle on the 
order of 24 degrees. The other surface 39 of each tooth extends downwardly 
at an angle approaching perpendicular to the surface 36. 
Above and slightly spaced axially from the lower cam member 19 is the upper 
cam member 21 which also is formed with a central bore 40 encircling the 
cylindrical portion 24a of the clutch element 24 and a surface 43 facing 
downwardly to oppose the surface 36 of the lower cam member. Equally 
spaced around the bore 40 are three teeth 41 which have inclined cam 
surfaces 26 mating with the surfaces 25 on the teeth 38 (see also FIGS. 7 
and 8) and sharply downwardly extending surfaces 42 opposing the surfaces 
39 on the teeth 38. Disposed between the cam members 19 and 21 is an 
annular wave spring which constitutes the resilient means 20 and acts 
between opposed annular surfaces 36 and 43 on the margins of the cam 
members to urge the upper cam member, which is slidable on the cylindrical 
portion 24a of the clutch element 24, upwardly and bring the friction 
surface 22 on the upper cam member into engagement with the friction 
surface 23 on the clutch element 24. This couples the shaft 11 to the 
blades 12 through the clutch element 24 and the cam members 19 and 21. The 
ramp or cam action of the inclined surfaces 25 and 26 produces a 
self-energizing effect which tends to increase the force between the 
friction surfaces 22 and 23 and correspondingly increase the coupling 
action between the shaft and the blades. Preferably, the friction surface 
22 on the upper side of the upper cam member 21 is formed by an annulus 44 
of friction material bonded to the upper cam member. 
In its preferred form, the actuator 16 is self-energizing in the same 
general manner as the clutch 15. Thus, the actuator includes two sheet 
metal rings 45 and 46 concentric with the shaft 11 and formed with one or 
more pairs, herein three, of opposed inclined surfaces or ramps 47 and 48. 
The resilient means 17 urges the rings relative to each other so that 
ramps 47 on the upper ring 45 tend to ride up relatively on the ramps 48 
on the lower ring 46. This action produces a progressively increasing 
force greatly exceeding the force of the resilient means 17. As seen most 
clearly in FIG. 9, the upper ring 45 also includes high flats 49 at the 
upper end of each ramp 47, downwardly inclined portions 50 following each 
high flat and low flats 51 connecting the portions 50 and the next one of 
the ramps 47. The lower ring 46 is identical in shape to the upper ring 45 
and includes high flats 52, downwardly inclined portions 53 and low flats 
54, all generally opposing the corresponding portions of the upper ring. 
As indicated at 55 in FIGS. 4 and 5, the high flats 49 of the upper ring 45 
of the actuator 16 are spot welded to a ring 56 which is fixed to the 
portion 13 of the frame of the lawn mower and encircles the shaft 11 (see 
also FIGS. 1 and 2), the upper ring thereby being stationary relative to 
the mower frame. The low flats 54 of the lower ring 46 are spot welded at 
57 to a radially outwardly projecting flange 58 on the lower end of a 
sheet metal cylinder 59 surrounding the upper cam member 21 (see FIGS. 1 
and 2). The cylinder 59, and hence the lower ring 46, is permitted to turn 
relative to upper ring 45 as limited by U-shaped clips 60 (FIGS. 4 and 5) 
loosely surrounding the ramps 47 and 48 and spot welded at 61 to the ramp 
47. An inwardly projecting flange 62 on the upper end of cylinder 59 
extends over the outer margin of the friction surface 22 on the upper cam 
member 21. When the actuator 16 is energized, the flange 62 pressed on the 
friction surface 22 and forces the upper cam member 21 down against the 
action of the wave spring 20 to move the friction surface 22 away from the 
opposing surface 23 on the clutch element 24 to disengage the clutch 15. 
At the same time, the under surface 63 of the flange frictionally engages 
the friction surface 22 to retard the rotation of the upper cam member 21 
and, through the coaction of the surfaces 39 and 42 on the cam members 19 
and 21, stops the rotation of the blades 12, the flanges 62 and the 
surface 22 constituting the brake 14. 
Herein, the lower ring 46 of the actuator 16 is urged in the energizing 
direction (to the left in FIG. 4 as indicated by the arrow 64) by the 
resilient means 17 which may, as shown in FIG. 3, be a compression spring 
acting between a portion 65 of the lawn mower frame and a finger 66 
projecting laterally from the lower flange 58 on the cylinder 59 to urge 
the finger in the direction of the arrow 67. In this manner, the spring 17 
normally urges the ramp 48 on the lower ring 46 down on the ramp 47 on the 
upper ring 45 as illustrated in FIG. 4 and causes the flange 62 on the 
cylinder 58 to press down on the friction surface 22 of the upper cam 
member 21 thereby to disengage the clutch 15 and prevent rotation of the 
blades 12. In order to disengage the brake 14 and engage the clutch 15 so 
that the shaft 11 drives the blades 12, the manual member 18 is a cable 
anchored at one end to the finger 66 and extending to the operating 
station of the mower such as at the handles of the mower. When the 
operator of the mower is at the operating station, he holds a suitable 
part such as a lever (not shown) which pulls the cable 18 in a direction 
to turn the lower ring 46 counterclockwise as viewed in FIG. 3 (see arrow 
68 in FIG. 3 and arrow 69 in FIG. 5) against the action of the spring 17 
thereby to move the ramp 48 on the lower ring 46 of the actuator up on the 
ramp 47 of the upper ring 45 to the position shown in FIG. 5 and this 
releases the brake 14, engages the clutch 15 and the shaft 11 thereby 
rotates the blades 12. Because of the self-energizing action of the 
actuator 16, the spring 17 need only exert a comparatively light force to 
energize the actuator and, thus, only a similarly light force need be 
applied to the cable 18 to deenergize the actuator. 
With the foregoing arrangement, the operation may best be understood with 
the assembly starting in a condition in which the lawn mower engine is 
running to drive the shaft 11 but the actuator 16 is energized as shown in 
FIGS. 1 and 4 so that the flange 62 presses down on the friction surface 
22 on the upper side of the upper cam member 21 to disengage this surface 
from the friction surface 23 of the clutch element 24. In this condition, 
the surface 63 of the flange 62 and the friction surface 22 of the upper 
cam member 21, these surfaces constituting the brake 14, hold the upper 
cam member against rotation and the sharply inclined surfaces 39 and 42 on 
the teeth 38 and 41 of the cam members 45 and 46 are in engagement as 
shown in FIG. 7 to prevent the lower cam member 17 and hence the blades 12 
from rotating. When the operator desires to use the mower, he goes to the 
operating station of the mower and moves, with light force, a lever or the 
like (not shown) to pull the cable 18 in the direction indicated by the 
arrow 68 in FIG. 3 to turn the lower ring 46 of the actuator 
counterclockwise against the action of the spring 17. As a result, the 
lower ring 46 of the actuator 16 turns to the right (see arrow 69 in FIG. 
5) so that the ramps 47 on the ring 45 no longer tend to climb relative to 
the ramps 48 on the ring 46 and the rings of the actuator 16 assume 
generally the positions illustrated in FIG. 5. The flange 62 on the 
cylinder 59 thereby moves up as shown in FIG. 2 and permits the wave 
spring 20 to urge the upper cam member 21 upwardly so that the friction 
surfaces 22 and 23 engage and the upper cam member begins to turn with the 
shaft 11. The ramps 26 on the teeth 41 of the upper cam member thus ride 
up on the ramps 25 on the teeth 38 of the lower cam member 19 (see FIG. 8) 
and this produces a progressively increasing force or self-energizing 
effect which forces the upper cam member 21 upwardly to engage fully the 
friction surface 22 of the upper cam member with the friction surface 23 
of the clutch element 24. This results in a progressively self-energizing 
of the clutch 15 which couples the shaft 11 and the lower cam member 19 
and rotates the blades 12. 
When the operator leaves the operating station of the lawn mower, the cable 
18 is released automatically and the spring 17 becomes effective to turn 
the lower ring 46 of the actuator 16 clockwise as indicated by the arrow 
67 in FIG. 3 and the arrow 64 in FIG. 4. As a result, the ramp 48 on the 
lower actuator ring 46 rides down on the ramp 47 on the upper ring 45 (see 
FIG. 4) and this produces a self-energizing effect of the actuator 16 to 
force the lower ring 46 downwardly so that the flange 62 on the cylinder 
59 presses down on the friction surface 22 of the upper cam member 21 and, 
as shown in FIG. 1, the flange 62 forces the upper cam member 21 down 
against the action of the wave spring 20 and disengages the friction 
surface 22 and 23 of the clutch 15. At the same time, the lower surface 63 
of the flange 62 frictionally engages the margin of the surface 22 to 
retard the upper cam member 21. This causes the surfaces 39 and 42 on the 
teeth 38 and 41 of the cam members 19 and 21 to engage and stop rotation 
of the lower cam member 19 and thus the rotation of the blades 12. 
FIGS. 10, 11 and 12 illustrate a modified form of the cam members 19' and 
21', similar parts being indicated by the same but primed reference 
characters. This form includes the provision of means for preventing the 
accidental application of an initiating force to the clutch 15 when the 
latter is disengaged so that the clutch can only be engaged by the 
manually operable element 18. Thus, this means prevents either one of the 
cam members being turned by hand relative to the other one which would, if 
permitted, initiate the self-energization of the clutch by virtue of the 
surface 26' beginning to ride up the surface 25'. 
Herein, this means comprises at least one abutment 70 on one of the cam 
members 19' and 21' and at least one recess 71 formed in the other cam 
member with the abutment and the recess being positioned so that the 
abutment is received in the recess when the generally axial surfaces 39' 
and 42' of the teeth 38' and 41' are in engagement, that is, when the 
elements of the clutch and brake assembly are in the stop condition. In 
the form shown in the drawings, there are three abutments 70 in the form 
of lugs depending from the flat surface 43' on the underside of the upper 
cam member 21' and are spaced equidistantly around the bore 40'. Each lug 
is disposed between two adjacent teeth 41' and are generally rectangular 
in cross section, being tapered downwardly slightly as shown best in FIGS. 
11 and 12. The inner side of the lug is flush with the wall of the bore 
40' and the width of the lug is approximately the same as the width of the 
inclined surfaces 26'. Similarly, three recesses 71 in the form of radial 
slots are formed in the surface 36' of the lower cam member 19' and are 
disposed between the teeth 38' at positions corresponding to the positions 
of the lugs 70. The grooves 71 extend radially inwardly from the bore 37' 
of the cam member 19' and their shape is generally complemental to that of 
the lugs although the grooves preferably are slightly wider than the lugs 
to insure that the lugs seat in the grooves when the surfaces 39' and 42' 
engage each other. 
With the foregoing arrangement, the lugs 70 are seated in the recesses 71 
when the parts of the clutch and brake assembly are in the stop condition, 
that is, when the generally axial surfaces 39' and 42' of the cam members 
19' and 21' are in engagement as shown in FIG. 11. In this condition, the 
lugs prevent the cam members from being inadvertently turned relative to 
each other such as might occur if there is an attempt to turn the blade 12 
manually. Thus, the lugs 70 in cooperation with the recesses 71 prevent 
accidental self-energization of the clutch. When the cable 18 is pulled to 
permit energization of the actuator 16, however, the spring 20' moves the 
cam member 21' up thus lifting the lugs out of the recesses so that the 
inclined surface 26' may ride up the inclined surface 25' as shown in FIG. 
12 and the self-energization of the clutch is initiated as described 
above. 
In the event that it is desirable to reduce the friction of the actuator as 
results from the self-energization of the latter, a modified actuator 16' 
may be used as illustrated in FIGS. 13 through 16 in which similar parts 
are indicated by the same but primed reference characters. Such reduction 
of friction is achieved by interposing a ball 72 between the inclined 
self-energizing surfaces of the actuator so that one surface in effect 
rolls rather than sliding up the other surface. 
In the form illustrated in the drawings, the actuator 16' includes a sheet 
metal upper ring 56' which is welded to the frame 13' and which is 
cup-shaped in that it comprises a flat annular portion 73 encircling the 
flange 27 and a cylindrical skirt 74 depending from the periphery of the 
annular portion. Struck downwardly from the annular portion are three 
flanges 47' which are spaced equidistantly around the ring 56' and which 
are disposed radially inwardly of the skirt 74. As shown in FIGS. 15 and 
16, the bottom edges 75 of the flanges 47' are inclined and constitute one 
set of the self-energizing surfaces of the actuator. 
A sheet metal cylinder 59' is disposed inside the flanges 47' and, as in 
the case of the form shown in FIG. 1, an annular flange 62' projects 
radially inwardly over the marginal portion of the friction surface 22. 
Projecting radially outwardly from the lower end of the cylinder is an 
annular flange 58' and struck upwardly from the latter are three short 
flanges 48' which are generally longitudinally alined with the flanges 
47'. The upper edges 76 (FIGS. 15 and 16) of the flanges 48' are inclined 
at the same angle as the edges 75 and oppose the latter to constitute the 
other set of self-energizing surfaces of the actuator. Disposed between 
each pair of edges 75 and 76 is a ball 72 and the balls are contained 
radially by the skirt 74 and the cylinder 59' (See FIG. 13) and are 
contained circumferentially by projections 77 and 78 on the ends of the 
flanges 47' and 48' respectively (See FIGS. 15 and 16). An arm 66' 
projects outwardly from the flange 58' through a slot 79 in the skirt 74 
and the cable 18 is connected to the outer end of this arm. 
In the form of actuator shown in FIGS. 13 through 16, the yieldable means 
which exerts the force for initiating self-energization of actuator 16' is 
contained within the body of the actuator and also serves to hold the 
cylinder 59' and its associated parts in place relative to the ring 56'. 
Thus, this means comprises three contractile springs 17' each disposed 
between one pair of flanges 47', 48' and the adjacent pair of flanges and 
each having one end anchored to a tab 80 on the ring 56' and the other end 
anchored to a tab 81 on the flange 58'. The springs 17' are inclined in a 
direction to initiate self-energization, that is, to urge the cylinder 59' 
to turn clockwise as viewed in FIG. 14 (to the left in FIGS. 15 and 16). 
The operation of the form shown in FIGS. 13 through 16 is basically the 
same as that shown in FIGS. 1 through 9. Thus, with no one at the 
operating station of the mower, the springs 17' initiate the 
self-energizing action of the actuator 16' by starting the cylinder 59' to 
turn so that the edges 76 of the flanges 48', through the medium of the 
balls 72, roll down on the edges 75 of the flanges 47'. This forces the 
cylinder and its associated parts axially downwardly whereby the flange 
62' presses down on the friction surface 22 to disengage the clutch 15 and 
to brake the blade 12, the parts of the actuator then being in the 
position shown in FIG. 15. When the operator pulls the cable 18, the edge 
76 of the flange 48' rolls up the edge 75 of the flange 47' as shown in 
FIG. 16 raising the flange 62' to disengage the brake 14 and engage the 
clutch 15 so that blade 12 turns. Small tabs 82 are bent in from the lower 
edge of the skirt 74 and underlie the flange 58'. These tabs merely help 
to hold the parts of the actuator 16' in place during assembly. Once 
assembled, however, the flange 58' always is spaced from the tabs 82 as 
the actuator is energized and deenergized. 
With the clutch-brake assembly 10 described above, the assembly 
automatically disengages the shaft 11 from the blades 12 as soon as the 
operator leaves the operating station of the mower while permitting the 
engine of the mower to continue to run but holding the blades 12 against 
turning. The use of the self-energizing actuator 16 produces a strong and 
effective force to accomplish this. To operate the mower, the operator 
merely exerts a low force at the operator station to pull the cable 18 
against the action of the spring 17 and this deenergizes the actuator 10, 
disengages the brake 14 and engages the clutch 15 with the result that the 
shaft 11 drives the blades 12. The end result is a clutch-brake system 
which safely disables the blades 12 when the operator leaves the operating 
station, which affords the operator a simple and low-force means for 
coupling the shaft 11 and the blades 12 when the operator is at the 
operating station and which is comparatively inexpensive.