Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF THE INVENTION
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Field of the Invention
The invention relates to clutches, and particularly,
to clutches which are operated automatically by centrifugal
force at a predetermined speed of rotation so as to connect a
driving member or load. More particularly, the invention
relates to an improved rotor assembly of a centrifugal clutch
in which a pair of clutch shoes are pivotally mounted on a
novel integral hub collar and pivot pin assembly.
Description of the Prior Art
There are numerous types and arrangements of centri-
fugal clutch constructions in which pivotally mounted clutch
shoes are retained in retracted position by springs or other
retaining means until sufficient centrifugal force acts on the
; shoes during rotation of the clutch rotor to overcome the
retaining force of the springs. The clutch shoes then pivot
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1 and swing outwardly to drivingly engage a concen-trically
located clutch housing or drum.
Many of these clutch constructions have a pair of
arcuate-shaped clutch shoes which are pivotally mounted on a
backing plate or drive flange and arranged in an end-to-end
relationship with respect to each other. The backing plate or
drive flange is fixed to a drive shaft or hub for rotation with
the drive shaft. These clutch shoes have various spring
arrangements for biasing the shoes toward retracted position,
which spring-retaining tensions are overcome by centrifugal
force acting on the shoes, whereupon the clutch shoes pivot out-
wardly and engage the driven member.
There are many types of such centrifugal clutches
which have proven satisfactory for their intended purpose.
~ost of these known clutches use a simple beam-type mounting
arrangement for the clutch shoes, wherein a pivot pin is sup-
ported on both ends by a pair of backing plates or the like.
The pins extend through a circular opening formed in and adja-
cent to one end of the clutch shoes for pivotally mounting the
shoes. Other types of clutches use a cantilever-type mounting
arrangement in which the pivot pin is supported at only one end
on the backing plate. In both types of constructions, the pin
projects through a circular opening in the clutch shoe. Vari-
ous bushing assemblies may be telescopically mounted on the
pivot pins and located within the shoe mounting openings to
provide various pivot arrangements.
These clutch constructions have the disadvantage of
limiting the outside diameter of the drive shaft with respect
to the over-all dimensions of the clutch shoe and clutch dia-
meter, since considerable metal mass is required for the rotorhub and clutch to provide the pivotal mounting of the clutch
shoe on the rotor hub or backing plates. These constructions
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1 also require the clutch shoes to be spacedfarther outward from
the axis of the clutch, thereby increasing the over-all diameter
of the clutch due to the extra metal required adjacent the inner
arcuate edge of the shoes to form the full circular pivot pin
opening with sufficient surrounding metal thickness to withstand
the repeated shocks and stresses which are exerted on the clutch
shoe during engagement with the driven clutch member.
Other clutch constructions have clutch shoes which are
mounted on pins which extend outwardly from a backing plate in
which the shoes are not captured by the pins but have a pivotal
sliding movement with respect thereto, as shown in United States
Patent Nos. 1,873,561 and 3,026,980. This type of clutch pro-
vides different operating characteristics than those clutches in
which the shoes are captured by their pivot pi.ns, since the
clutch shoes move outwardly and away from the support pin upon
engaging the driven housing.
These various clutch constructions also require addi-
tional components, such as the backing plate or plates and
separate pins, which must be manufactured and mounted thereon by
various manufacturing methods, all of which increase the cost of
the clutch, and in certain situations, present maintenance
problems.
Thus, the need has existed for a centrifugal clutch
construction of the type in which the clutch shoes are captured
by their pivot pins, preventing movement of the shoe end away
from the pin without requiring the heretofore relatively large
metal masses to form the pivot pin mounti.ng opening in the
clutch shoe, and also a clutch construction which enables a
maximum outside diameter drive shaft tG be used without increas-
ing the over-all diameter of the clutch while still obtaining
the same torque characteristics as possible with those clutches
which are limited to relatively smaller diameter drive shafts.
1 There is no known centrifugal clutch construction of
which I am aware which provides for pivotally mounting the
clutch shoes on an integral hub collar and pivot pin member by
use of a discontinuous pivot pin opening formed in the clutch
shoe which captures the clutch shoes on their pivotal mounting
pins, and which enables a maximum outside diameter drive shaft
to be used with the same size clutch shoe he~etofore used,
thereby achieving the same operating torque characteristics.
SUMMARY OF THE IN~ENTION
Objectives of the invention include providing an
improved centrifugal clutch construction having a pair of clutch
shoes arranged in an end-to-end relationship with respect to
each other and pivotally mounted on an integral hub collar and
pivot pin member which eliminates the separate pivot pins and
backing plate components heretofore required for the pivotal
mounting of the clutch shoes; providing a clutch construction
which eliminates the relatively large metal mass adjacent an
end of the clutch shoe hereto-fore required for forming a pivot
pin mounting opening in the shoe, by the use of a discontinuous
pivot pin mounting opening in the shoe end having an opening
forming arcuate surface greater than 180 and less than 360,
and in this mounting arrangement captures the clutch shoe on
the pivot pin, preventing any movement or disengage~ent of the
clutch shoe from the pivot pin; providing a clutch construction
which enables a maximum diameter drive shaft to be used without
affecting the over-all diameter of the clutch while achieving
the same clutch shoe torque characteristics as in prior con-
structions requiring a smaller drive shaft diameter; providing
such a centrifugal clutch construction which is of a relatively
simple arrangement, easy to manufacture and assemble, sturdy
and durable in use, which eliminates difficulties encountered
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1 with other clutch constructions, which is light in weight,
which achieves the objectives indicated, and which solves prob-
lems and satisfies needs existing in the art.
These objectives and advantages are obtained by the
improved centrifugal clutch construction, the general nature of
which may be stated as including a driven clutch member; pivot
collar means adapted to be mounted on a drive shaft for rota-
tion with said drive shaft, th.e collar means having a cylindri-
cal-shaped sleeve formed with a bore and a pair of diametri-
cally opposed projection means mounted externally on the sleeveand extending along and parallel with the axis of said sleeve,
said projection means each having a cylindrical shape, the
outer circumference of which lies in abutting or overlapping
relationship wi.th respect to the outer circumference of the
cylindrical-shaped s].eeve at the mounting location therebetween
when viewed in transverse cross section; a pair of clutch shoe
means, each shoe means being pivotally mounted on a respective
one of the pair of projection means for pivotal movement out-
wardly toward and against the driven clutch member under the
influence of centrifugal force from retracted to extended
positions; and discontinuous opening means formed in an end of
each of the clutch shoe means for receiving the projection
means therein to pivotally mount the shoe means on said pro-
jection means, said opening means having a partial circular
cross-sectional configuration of greater than 180 and less
than 360 complementary to the cross-sectional configuration
of the projection means.
- BRIEF DESCRIPTION OF THE DRAWINGS
.
A preferred embodiment of the invention - illustra- ..
tive of the best mode in which applicant has contemplated
applying the principles - is set forth in the following
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1 description and shown in the drawings and is particularly and
distinctly pointed out and set forth in the appended claims.
Figure 1 is an exploded perspective view of a portion
of the improved centrifugal clutch construction;
Fig. 2 is a fragmentary plan view of one of the
clutch shoes shown pivotally mounted on one of the pivot collar
projections;
Fig. 3 is a reduced top plan view of the improved
clutch construction with the clutch housing and hub shown in
section and the clutch shoes in disengaged position;
Fig. 4 is a view similar to Fig. 3 with the clutch
shoes shown in engaged position;
Fig. 5 is an enlarged sectional view taken on line
5-5, Fig. 3, with the clutch shown mounted on a drive shaft;
Fig. 6 is an enlarged sectional view similar to Fig.
5 taken on line 6-6, Fig. 4, with the clutch shown mounted on a
drive shaft; and
Fig. 7 is a fragmentary view similar to Fig. 2 showing
a prior art clutch shoe pivotal mounting arrangement.
Similar numerals refer to similar parts throughout
the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The improved clutch construction is indicated gener-
ally at 1, and is shown in assembled condition in Figs. 3 and 4,
and is shown mounted on a power drive shaft 2 in Figs. 5 and 6.
Clutch 1 includes a rotor assembly 3 and a driven clutch member
or housing 4. Clu~ch 1 is shown in disengaged position in
Figs. 3 and 5, and in engaged position with housing 4 in Figs.
4 and 6.
Housing 4 is shown as a pulley clutch housing combin-
ation having a V-groove pulley member 5 which is connected to a
1 hub flange wall 6 of cup-shaped housing 4 by an annular spacer
ring 7. The inner cylindrical surface 8 of housing wall g
provides the coupling surface for drivingly connecting clutch
housing 4 with rotor assembly 3. Housing 4 and V-groove pulley
5 may have various configurations and arrangements than that
shown in the drawings and may be adapted to be operatively
engaged with mechanisms other than a V-groove pulley belt
without departing from the concept of the invention.
A bearing ring 10 is telescopically mounted on the
outer surface 11 of a cylindrical hub 12 and concentrically
within a central mounting opening 13 of pulley member 5. Bear-
ing ring 10 enables hub 12 and rotor assembly 3 which is mounted
on hub 12, to rotate freely with respect to housing 4 and
pulley 5 until coupling engagement is achieved between rotor
assembly 3 and housing surface 8. Hub 12 is mounted on and
secured to drive shaft 2 by a key-keyway arrangement 13a.
A portion of the main components of rotor assembly 3
is shown in Fig. 1 in an exploded condition. Rotor assembly 3
includes a pivot collar 15, a pair of clutch shoe assemblies 16
pivotally mounted on collar 15, and a pair of retaining springs
17. Only one of the clutch shoe assemblies 16 is shown in
exploded condition in Fig. 1. Each shoe assembly 16 includes a
pair of similar, preferably identical, half-shoe sections 18 and
19 with a spacer member 20 being sandwiched therebetween. Shoe
sections 18 and ]9 each have a generally arcuate configuration
with a smooth convexly shaped outer surface 21 and a comple-
mentary concavely shaped inner surface 22. The outer swinging
end of each shoe section is formed with a stepped edge 23.
Spacer 20 has an arcuate configuration similar in size
and shape to shoe sections 18 and 19. Spacer 20 includes a
convex outer surface 25 and a concave inner surface 26 which are
in axial alignment with outer convex surfaces 21 and inner
1 concave surfaces 22, respectively, of shoe sections 18 and 19
when spacer 20 is mounted therebetween. Shoe sections 18 and
19 and spacer 20 are joined together by a pair of pins 29 or
other fastening means which extend through aligned holes 30 and
31 formed in shoe sections 18 and 19 and spacer 20, respectively.
The ends of outer convex surfaces 25 of spacers 20
are formed with U-shaped recesses 33 into which hook-shaped
ends 34 of retaining springs 17 are located when the clutch is
in assembled position to bias shoe assemblies 16 toward
retracted position. The outer ends of spacer 20, including
U-shaped recesses 33, are exposed beyond the ends of shoe sec-
tions 18 and 19 (Fig. 2) due to stepped edges 23 of the shoe
sections to enable springs 17 to be mounted thereon.
An arcuate-shaped strip of friction material 36 is
mounted on and extends between the outer convex surfaces 21 and
25 of shoe sections 18 and 19 and spacer 20 to provide a coup-
ling surface which engages inner drum wall surface 8 for coup-
ling engagement between drive rotor assembly 3 and housing 4.
Friction material 36 may be attached by an adhesive or other
fastening means.
In accordance with the invention, pivot collar 15
includes a sleeve 38 having a cylindrical outer surface 39 and
a concentric cylindrical inner surface 40 which forms ~n
interior bore 41. A pair of generally cylindrical projections
43 are mounted diagonally opposite of each other on outer sur-
face 39 of sleeve 38 and extend axially therealong~ with the
longitudinal axes of projections 43 being parallel to each other
and to the longitudinal axis of sleeve 38. Projections 43
preferably are formed integral with sleeve 38 by sintering,
casting, machining or similar procedures. If desired3 projec-
tions 43 may be separate components which are attached to sleeve
38 by welding, brazing, etc.
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1 Projections 43 preferably are identical to each other
and include a nearly cylindrical outer surface 44 which has a
circumferential length greater than 180 and less than 360,
preferably in the vicinity of 270 (Fig. 2). Outer surfaces 44
of projections 43 lie in overlapping or at least abutting rela-
tionship with the outer surface 39 of sleeve 38 at their points
of attachment, as can be seen in Pigs. 1-4. This relationship
moves the pivot point for the clutch shoes as close as possible
to the axial center of sleeve 48. Projections 43 are connected
to outer sleeve surface 39 by a connecting base 45, Base 45
has a pair of straight side walls 46, which extend generally
radially with respect to the axis of collar 15 and extend be-
tween and axially along outer sleeve surface 39 and projection
surfaces 44. Projections 43 may be formed with a central opening
48 which reduces the weight of the collar without sacrificing
strength.
Collar 15 is telescopically mounted on hub 12 within
cup wall 9 of housing 4 with a force fit so as to rotate with
hub 12. Collar 15 is located between a pair of side plates 42
which have an annular configuration. Side plates 42 are held
in position by a pair of snap rings 47 which are located within
a pair of circumferential grooves 49 formed in and extending
about surface 11 of hub 12 (Figs. 5 and 6).
In further accordance with the invention, a curved
hook-like formation 50 is formed on one end of each shoe section
18 and 19, opposite stepped edges 23. Hook formations 50 form
discontinuous openings 51 at the end of each shoe section.
Openings 51 are defined by concavely shaped, generally cylindri-
cal surfaces 52 which have radi,i of curvature and arcuate
lengths complementary to outer surfaces 44 of projections 43.
Surfaces 52 of discontinuous openings 51 have arcuate lengths
greater than 180 and less than 360 as do surfaces 44 of
L2
1 pivot projections 43.
A concavely shaped surface 54 also is formed in one
end of spacer 20, and has a radius of curvature equal to that
of discontinuous openings 51 so as to conform generally to the
curvature of surfaces 52 of shoe sections 18 and 19.
In assembled condition, shoe assemblies 16 are pivot-
ally mounted on collar 15 by telescopic engagement of sleeve
projections 43 within discontinuous shoe section openings 51.
Springs 17, by means of the hooked end engagements in spacer
recesses 33, bias the pivotally mounted shoe assemblies 16
toward the retracted position of Figs. 3 and 5. The concaved
inner surfaces 22 and 26 of shoe sections 18 and 19 and spacer
segment 20 abut outer surface 39 of cylindrical sleeve 38 when
in retracted unactuated position preventing any further inward
pivotal movement of the shoe assemblies.
The basic operation of clutch 1 is similar to many
centrifugally actuated clutch constructions. Shoe assemblies
16 attempt to pivot radially outwardly from their retracted
positions of Figs. 3 and 5 under the influence of centrifugal
force as the rotational speed of shaft 2 increases. The pre-
determined resistance of springs 17 retains the shoes in disen-
gaged position until shaft 2 reaches a predetermined engagement
speed, When approaching the engagement speed, clutch shoe
assemblies 16 move outwardly, pivoting about cylindrical pro-
jections 43 until friction material strips 36 drivingly engage
drum wall surface 8, as shown in Figs. 4 and 6. This coupling
engagement rotates housing 4 and connected V-groove pulley 5
with rotor assembly 3 to operatively drive a pulley V-belt
(not shown) extending about and seated within the V-groove of
pulley 5. The engagement speed of the clutch is dependent upon
a number of known and determinable factors, such as the weight
of shoe assemblies 16, the load rate of springs 17, location
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1 of pivot projections 43, etc.
Clutch shoe assemblies 16 will maintain their driving
engagement with driven clutch member 4 until the speed of
shaft 2 decreases to a predetermined level, whereupon the cen-
trifugal force exerted on the shoes is overcome by the biasing
force of springs 17. At the disengagemerlt speed, springs 17
will retract the shoes from the engaged position of Figs. 4 and
6 to the disengaged position of Figs. 3 and 5.
In accordance with one of the main features of the
invention, shoe assemblies 16 will pivot on collar 15 about
projections 43, with projection surfaces 44 slidably engaging
surfaces 52 which form the discontinuous openings 51. The
particular clutch shoe mounting arrangement on projections 43
of collar 15 provides advantages not believed achieved with
known prior clutch constructions. The discontinuous openings 51
of the clutch shoes and their engagement with the nearly
cylindrical complementary outer surfaces of projections 43
maintain the pivotally mounted end of the clutch sh~es in a
captured state with respect to pivot projections 43. This
captured arrangement permits only pivotal movement of the
clutch shoes with respect to their mounting pin, as is achieved
in a usual clutch construction which has a continuous or com-
plete circular pivot opening formed in the clutch shoes through
which circular pivot pins or bushings extend. Since the discon-
tinuous shoe openings and complementary generally cylindrical
surfaces of the pivot projections are greater than 180, the
shoes are captured by the pins and will not move away from the .
pivotal contact therewith. This captured state is not achieved
in other clutch constructions wherein the clutch shoes pivotally
and slidably move about and away from a pivot projection which
is engaged within a groove formed in the clutch shoes of less
than 180.
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1 This discontinuous opening and partial cylindrical
projection mounting arrangement (shown particularly in Fig. 2)
has the further advantage of enabling the clutch shoes to be
mounted closer to the clutch axis or pivot collar or hub,
thereby achieving a smaller outer diameter with the same size
drive shaft than in prior clutch constructions. Alternatively,
this arrangement enables the oveT-all outer diameter of the
clutch to remain the same as in prior clutch constructions,
while enabling a larger outer diameter drive shaft to be used.
This advantage is possible since the internal diameter of collar
lS, and correspondingly, that of hub 12, can be increased due
to the less space required to pivotally mount the shoes in a
captured state. This feature is shown by a comparison of Fig.
2 with the prior art arrangement of Fig. 7.
The prior art construction of Fig. 7 also shows the
additional metal that is required for pivotally molmting the
clutch shoes in a captured position on the hub or backing
plate. Likewise, this prior construction shows the additional
components that are required for the mounting of the clutch
shoes. A comparison of Figs. 2 and 7 further shows the larger
drive shaft diameter that can be used for the same diameter
prior art clutch.
Another advantage and feature of improved clutch
construction 1 is the use of the end edge 55 of curved hook
formation 50 as a stop to prevent damage to outer metal sur-
faces 21 and 25 of the shoe sections and spacer upon complete
wearing away of friction strip 36. End edge 55 abuts outer
surface 39 of cylindrical sleeve 38, as shown in dot-dash
lines Fig. 2~ after a predetermined outward pivotal movement
distance of the clutch shoes, which distance will correspond to
the maximum amount of wear of friction strips 36.
Stop ~`dges 55 thereby prevent any further pivotal
1 outward movement of the shoes after a predetermined amount of
wear to friction strips 36, preventing any contact of the outer
metal surfaces of the shoes with housing wall surface 8. After
reaching this maximum friction material wear condition, the
clutch will begin to slip excessively or will not achieve coup-
ling engagement, indicating that replacement of friction strips
3~ is required.
Accordingly, the improved centrifugal clutch provides
a construction which is simplified, e-ffective, safe, inexpensive,
efficient, strong and durable in use, which enables larger
torque characteristics to be achieved with less metal than in
prior constructions, which eliminates separate backing plates,
pivot pins and related components which are subject to breakage
and maintenance, which enables a larger drive shaft diameter to
be used with the same size clutch shoes and with the same outer
clutch dimensions than in prior constructions, which achieves
all the enumerated objectives, provides for eliminating diffi-
culties encountered with prior clutch constructions and devices,
and solves problems and obtains new results in the art.
In the foregoing description, certain terms have been
used for brevity, clearness and understanding, but no unneces-
sary limitations are to be implied therefrom beyond the require-
ments of the prior art, because such words are used for des-
criptive purposes herein and are intended to be broadly con-
strued.
Moreover, the embodiment of the improved construction
illustrated and described herein is by way of example, and the
scope of the present invention is not limited to the exact
details of construction shown or described.
Having now described the features, discoveries and
principles of the invention, the manner in which the improved
centrifugal clutch construction is constructed, assembled and
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1 operated, the characteristics of the new construction, and the
advanta~eous, new and useful results obtained; the new and
useful structures, devices, elements, arrangements, parts, and
combinations are set forth in the appended claims.
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