Title: Jaw clutch shock force damper system
Abstract: The jaw clutch damper system includes a damper which can be a disk spring which absorbs shock forces generated by rapid re-engagement of clutch plates of the clutch and dissipates energy of the shock forces in cooperation with the other components of the clutch, including a clutch spring, such that resulting shock forces exerted against rotatable members connected to the clutch are damped and reduced substantially in magnitude within a time interval before occurrence of a subsequent shock force.
Patent Number: 6,979,268 Issued on 12/27/2005 to Peters, et al.
| Inventors:
|
Peters; Jeremy D. (New Holland, PA);
Digman; Michael J. (Denver, PA)
|
| Assignee:
|
CNH America LLC (Racine, WI)
|
| Appl. No.:
|
722744 |
| Filed:
|
November 25, 2003 |
| Current U.S. Class: |
464/39; 192/56.61 |
| Intern'l Class: |
F16D 007/04 |
| Field of Search: |
464/38,39
474/70,903
56/DIG.6,DIG.15
267/161
192/566.1,56.R,698.1,107.C
|
References Cited [Referenced By]
U.S. Patent Documents
| 2291407 | Jul., 1942 | Talbert.
| |
| 2348717 | May., 1944 | Banker.
| |
| 2869697 | Jan., 1959 | Marshall.
| |
| 2869700 | Jan., 1959 | Bowden.
| |
| 3314257 | Apr., 1967 | Fosler et al.
| |
| 3491602 | Jan., 1970 | New.
| |
| 3934688 | Jan., 1976 | Sides et al.
| |
| 4062203 | Dec., 1977 | Leonard et al.
| |
| 4155228 | May., 1979 | Burgener, Jr. et al.
| |
| 4474275 | Oct., 1984 | Staedeli.
| |
| 5074703 | Dec., 1991 | Dawson.
| |
| 6128574 | Oct., 2000 | Dickhans.
| |
| 6241067 | Jun., 2001 | Höck.
| |
| Foreign Patent Documents |
| 1 945 002 | Mar., 1971 | DE.
| |
Other References
SAE Universal Joint and Driveshaft Design Manual, AE-7, Society of Automotive
Engineers, Inc., p. 304, TJ1079.S62 1979.
|
Primary Examiner: Binda; Greg
Attorney, Agent or Firm: Henkel; Rebecca
Claims
1. In a jaw clutch for transferring rotational power from a driving rotatable
member to a driven rotatable member, the jaw clutch including a first clutch plate
connected to one of the rotatable members for rotation therewith and movement along
a predetermined path relative thereto, and a second clutch plate connected to another
of the rotatable members for rotation therewith adjacent to an end of the path,
the clutch plates including teeth matingly engageable when the clutch plates are
in abutment for connecting the clutch plates for joint rotation, and a clutch spring
having a predetermined spring rate disposed for exerting a spring force against
the first clutch plate for holding the first clutch plate at the end of the path
in abutment with the second clutch plate, the clutch spring being yieldable to
a disengagement force greater than the spring force applied against the first clutch
plate in opposition to the spring force such that the first clutch plate will be
moved along the path away from the second clutch plate and the teeth of the clutch
plate connected to the drivingly rotated member will move in a ratcheting action
over the teeth of the clutch plate connected to the driven rotating member to generate
shock forces between the clutch plates having magnitudes substantially greater
than the magnitude of the disengagement force at time intervals which are a function
of a relative speed of rotation of the clutch plates, an improvement comprising:
a shock damper including a spring having a predetermined spring rate several
times greater than the spring rate of the clutch spring disposed in connection
with the second clutch plate in a position for absorbing a substantial portion
of energy of the shock forces generated between the clutch plates and then releasing
the energy so as to be at least partially dissipated by the clutch such that resulting
portions of shock forces exerted against the rotating members will be damped so
as to have maximum magnitudes equal to less than half of the magnitudes of the
shock forces generated between the clutch plates, while holding the second clutch
plate substantially stationary adjacent to the end of the path.
2. In the jaw clutch of claim 1, the spring of the shock damper comprising a
disk spring which is resiliently deformable from an initial shape to a deformed
shape by absorbing the energy of the shock forces, and which will return to the
initial shape by releasing the energy absorbed thereby.
3. In the jaw clutch of claim 2, the improvement further comprising the disk
spring being operable in cooperation with the clutch spring for cyclically transferring
at least a portion of the energy of the shock force between the clutch plates for
dissipating the energy.
4. In the jaw clutch of claim 1, the improvement comprising the spring rate of
the disk spring being at least ten times greater than the spring rate of the clutch spring.
5. In the jaw clutch of claim 1, the improvement comprising the spring rate of
the disk spring being at lest fifteen times greater than the spring rate of the
clutch spring.
6. In the jaw clutch of claim 1, the improvement comprising the spring rate of
the disk spring being between about 30,000 and about 40,000 pounds per inch and
the spring rate of the clutch spring being between about 2000 and about 3000 pounds
per inch.
7. In the jaw clutch of claim 1, the improvement comprising the spring rate of
the disk spring being between about 35,000 and about 38,000 pounds per inch and
the spring rate of the clutch spring being between about 2100 and about 2400 pounds
per inch.
8. In the jaw clutch of claim 2, the second clutch plate and the rotatable member
connected thereto being mounted on a sleeve supported on the rotatable member connected
thereto in fixed relation to the end of the path, the sleeve including a shoulder
extending therearound, and the improvement further comprising the disk spring being
disposed between the rotatable member connected to the second clutch plate and
the shoulder.
9. In a jaw clutch engageable for connecting a rotatable shaft and a rotatable
member supported thereon for joint rotation about an axis of the shaft, the clutch
being disengageable for allowing relative rotation of the shaft and the member,
the clutch including a first clutch plate mounted on the shaft for rotation therewith
and axial movement therealong, a second clutch plate mounted on the shaft and connected
to the member for rotation relative to the shaft, the clutch plates having axially
opposing teeth matingly engageable for joint rotation thereof, and a clutch spring
disposed for applying an axial spring force against the first clutch plate for
holding the opposing teeth in mating engagement, the clutch plates being movable
apart by application of a disengagement force between the teeth such that the opposing
teeth will rotate in ratcheting relation so as to alternatingly disengage and fully
or partially matingly re-engage to exert axial shock forces against the clutch
plates having magnitudes several times greater than magnitudes of the spring force
and the disengagement force, an improvement comprising:
a damper spring disposed between the second clutch plate and an element mounted
at an axially fixed location on the shaft, the damper spring having a spring rate
at least several times greater than a spring rate of the clutch spring so as to
hold the second clutch plate in a substantially stationary axial position when
only the spring force and the disengagement force are applied, and so as to absorb
at least a substantial portion of energy of the shock forces exerted against the
clutch plates and dissipate energy thereof in cooperation with the clutch spring
and the clutch plates such that resultant axial shock forces exerted against the
shaft will have maximum magnitudes of less than half the magnitudes of the shock
forces exerted against the clutch plates.
10. In the jaw clutch of claim 9, the improvement comprising the spring rate
of the damper spring being at least ten times greater than the spring rate of the
clutch spring.
11. In the jaw clutch of claim 9, the improvement comprising the spring rate
of the damper spring being at least fifteen times greater than the spring rate
of the clutch spring.
12. In the jaw clutch of claim 9, the improvement comprising the spring rate
of the damper spring being between about 30,000 and about 40,000 pounds per inch
and the spring rate of the clutch spring being between about 2000 and about 3000
pounds per inch.
13. In the jaw clutch of claim 12, the spring rate of the damper spring being
between about 35,000 and about 38,000 pounds per inch and the spring rate of the
clutch spring being between about 2100 and about 2400 pounds per inch.
14. In the jaw clutch of claim 9, the damper spring comprising a disk spring.
15. In a jaw clutch mounted on a shaft rotatable about an axis therethrough,
the clutch including a first clutch plate mounted on the shaft for rotation therewith
and axial movement therealong, a second clutch plate mounted on a sleeve around
the shaft and connected to a rotatable member for rotation about the shaft, the
sleeve having a shoulder therearound at a predetermined axial location, the clutch
plates having axially opposing teeth matingly engageable for connecting the shaft
and the member for driven rotation of one by the other, and a clutch spring disposed
for applying an axial spring force against the first clutch plate for holding the
opposing teeth in mating engagement, the clutch plates being movable axially apart
by application of a disengagement force between the teeth resulting from resistance
to rotation of the driven one of the shaft and the member such that the opposing
teeth will rotate in ratcheting relation wherein the teeth cyclically disengage
and fully or partially matingly re-engage so as to exert axial shock forces against
the clutch plates having magnitudes several times greater than magnitudes of the
spring force and the disengagement force, respectively, an improvement comprising:
a resilient shock damper including a disk spring disposed between the second
clutch plate and the shoulder, the disk spring having a spring rate sufficiently
greater than a spring rate of the clutch spring so as to hold the second clutch
plate substantially axially stationary when only the spring force and the disengagement
force are applied, and so as to absorb energy of the shock forces exerted against
the second clutch plate and release and redirect the energy through the clutch
plates to the clutch spring so as to be at least partially dissipated such that
any resulting shock forces exerted against the shaft will have magnitudes substantially
less than magnitudes of the shock forces exerted against the clutch plates.
16. In the jaw clutch of claim 15, the damper wherein the disk spring is resiliently
deformable from an initial shape to a deformed shape by absorbing the energy of
the shock forces and which will return to the initial shape by releasing the energy
absorbed thereby.
17. In the jaw clutch of claim 16, the improvement further comprising the disk
spring being operable in cooperation with the clutch spring for cyclically transferring
at least a portion of the energy of the shock forces to the clutch plates for dissipation
by relative movement thereof.
18. In the jaw clutch of claim 15, the improvement comprising the spring rate
of the disk spring being at least ten times greater than the spring rate of the
clutch spring.
19. In the jaw clutch of claim 15, the improvement comprising the spring rate
of the disk spring being at least fifteen times greater than the spring rate of
the clutch spring.
20. In the jaw clutch of claim 15, the improvement comprising the spring rate
of the disk spring being between about 30,000 and about 40,000 pounds per inch
and the spring rate of the clutch spring being between about 2000 and 3000 pounds
per inch.
21. In the jaw clutch of claim 15, the spring rate of the disk spring being between
about 35,000 and about 38,000 pounds per inch and the spring rate of the clutch
spring being between about 2100 and about 2400 pounds per inch.
Description
TECHNICAL FIELD
This invention relates generally to a jaw clutch engageable for connecting rotatable
members for joint rotation and disengageable for allowing relative rotation of
the members, and more particularly, to a jaw clutch including a shock force damper
for absorbing shock forces resulting from engagement of the clutch and dissipating
the forces over time in cooperation with other components of the clutch for damping
or reducing the intensity and magnitude of resultant forces exerted against the
rotating members.
BACKGROUND
It is well known to use jaw clutches including clutch plates having opposing
matingly
engageable or interlocking teeth for connecting rotatable members such as a shaft
and a sprocket or pulley for rotation of one by the other. Many such jaw clutches
include at least one clutch spring for exerting a spring force against the clutch
plates for holding the opposing teeth in engagement. The opposing teeth of such
clutches typically include opposing mating ramp surfaces which are slidable one
relative to the other by the exertion of a disengagement force therebetween in
opposition to and greater than the spring force, to cause the clutch plates to
move away from one another. Such disengagement force can result, for example, from
high torque conditions generated as a result of resistance to rotation of a driven
one of the rotatable members. If the disengagement force is great enough in magnitude
and duration to move the clutch plates out of mating engagement, the teeth of the
driving clutch plate can ratchet or move over the teeth of the other clutch plate
to allow rotation of the driving clutch plate relative to the other clutch plate.
As this ratcheting occurs, there are times when the teeth of the two clutch plates
are directly opposing so as to hold the clutch plates apart such that the clutch
spring stores a substantial amount of potential energy. Then, as the teeth of the
driven clutch plate pass the teeth of the other clutch plate and thus are no longer
opposing, the clutch plates are no longer held apart such that the stored potential
energy will be partially or fully released to drive the clutch plates together.
If this occurs abruptly or suddenly, such as due to fast rotation of the driving
clutch plate and/or abrupt stoppage or slow down of driven components, the clutch
plates can be rapidly driven together so as to exert a shock force therebetween
which can have a magnitude several times that of the spring force and the disengagement
force. If the ratcheting continues, the shock force can be exerted numerous times
or cyclically so as to have a repeating, hammering effect. The shock force can
be transmitted through the clutch components to the rotatable members and other
components such as supporting bearings, bushings, drive chains, belts, and the
like, and can be damaging thereto. Problems that have resulted include movements
of the rotatable members and associated components that result in accelerated wear
and breakage. The hammering effect can also loosen connected items such as hardware
and the like. Such clutches are often used to transmit relatively large amounts
of rotational power, for instance, for rotating feeder apparatus within the feeder
house of an agricultural combine, and thus, the spring force and disengagement
force can have a magnitude of 1000 pounds or more. The magnitude of resultant shock
forces exerted against the clutch plates and associated structure including shafts
and the like can be many times that, including up to 10,000 pounds.
Accordingly, what is sought is a shock force damping capability for
a jaw clutch which overcomes one or more of the problems set forth above.
SUMMARY
What is disclosed is a jaw clutch including a shock damper system or arrangement
that overcomes one or more of the problems set forth above. The jaw clutch is conventionally
operable for transferring rotational power from a driving rotatable member to a
driven rotatable member, and includes a first clutch plate connected to one of
the rotatable members for rotation therewith and movement along a predetermined
path relative thereto, and a second clutch plate connected to another of the rotatable
members for rotation therewith adjacent to an end of the path. The clutch plates
include teeth engageable in mating relation when the clutch plates are in abutment
for connecting the clutch plates for joint rotation. The clutch includes a clutch
spring disposed for exerting a spring force against the first clutch plate for
holding it at the end of the path in abutment with the second clutch plate, the
clutch spring being yieldable to opposing disengagement forces greater than the
spring force applied thereagainst through the first clutch plate so as to allow
the first clutch plate to move along the path away from the second clutch plate
to disengage the opposing teeth from the mating relationship and allow relative
rotation or ratcheting of the clutch plates and the storing and releasing of potential
energy by the clutch spring. If this occurs suddenly or abruptly, as discussed
above the opposing teeth can rapidly re-engage resulting in exertion of a high
shock force between the clutch plates. If this occurs repeatedly, the result can
be the potentially damaging hammering effect discussed above. The shock damper
of the invention is disposed in connection with the second clutch plate for damping
the resultant shock forces transferred to the rotatable members by absorbing at
least a substantial portion of the energy of the shock forces as they occur, and
releasing and dissipating the energy there over a period of time in cooperation
with the clutch components, preferably largely by movements of the clutch spring
and the first clutch plate while holding the second clutch plate substantially
stationary relative to the end of the path. As a result, the magnitude of shock
force transferred to the rotatable members is damped or reduced, and time period
of the dissipation corresponds to or is less than the interval or cycle time between
sequential ratcheting movements of the teeth, to thereby reduce the occurrence
and magnitude of the problems set forth above.
According to a preferred aspect of the invention, the shock damper includes
a disk spring which has a sufficiently high spring rate so as to remain substantially
rigid when the spring force and disengagement force are exerted thereagainst, but
which is resiliently deformable from an initial shape to a deformed shape by the
much higher magnitude of the impact created shock force, so as to absorb much of
the energy of the shock force, and then return to the initial shape by releasing
the energy. Also preferably, the disk spring is operable in cooperation with at
least the clutch spring as a system for cyclically transferring at least a portion
of the energy of the shock force between the clutch plates for dissipating the
energy, such that the resultant shock forces transferred to the rotating members
will be substantially damped or lessened in magnitude, preferably by at least half.
To achieve the desired damping effect while holding the second clutch plate substantially
stationary adjacent to the end of the path, the disk spring preferably has a spring
rate several times greater than a spring rate of the clutch spring. As a result,
for a disengagement force of a particular magnitude, displacement of the clutch
spring and the first clutch plate along the path will be a correspondingly number
of times greater than displacement of the disk spring and second clutch plate,
if any. And, since the spring rate of the disk spring is several times that of
the clutch spring, even when a shock force several times greater than the disengagement
force is exerted between the clutch plates, displacement of the disk spring and
the second clutch plate is minimalized.
As another preferred aspect of the present invention, the first clutch plate
is
mounted on a rotatable member which is a shaft, for rotation therewith and axial
movement relative thereto. The second clutch plate is mounted for rotation on the
shaft with the other rotatable member. The other rotatable member can be a second
shaft, or a sprocket partially encircled by a chain, or a pulley partially encircled
by a belt. The disk spring is preferably disposed between the second clutch plate
and an axially fixed member on the shaft. As a result of the high spring rate,
the damper will hold the second clutch plate substantially stationary with respect
to an axial path of movement of the first clutch plate. Here, it should be noted
that it is contemplated that under anticipated shock force levels, some very limited
axial movement of the second clutch plate and the rotatable member connected thereto
is anticipated and permissible, as long as such movement is within tolerance levels
for side play of the chain or belt used, or otherwise will not negatively affect
operation thereof.
According to a preferred aspect of the invention, the spring rate of the
disk spring is at least ten times greater than the spring rate of the clutch spring.
More preferably, the spring rate of the disk spring is at least fifteen times greater
than the spring rate of the clutch spring. As examples, for a jaw clutch used for
transferring rotatable power from a chain drive to a drive system within a feeder
house of an agricultural combine, a range of suitable values for the spring rate
of the disk spring can be between about 30,000 and about 40,000 pounds per inch
and the spring rate of the clutch spring between about 2,000 and about 3,000 pounds
per inch. More specifically, a satisfactory spring rate of the disk spring is about
36,800 pounds per inch and the spring rate for the clutch spring about 2,235 pounds
per inch. Of course, other spring rates may be more suitable for other applications,
it being most important to recognize that the spring rate for the shock damper
should be sufficiently greater than that of the clutch spring such that shock forces
will be damped and dissipated with only limited or controlled movement of the second
clutch plate and related rotating member, such that that clutch plate and rotating
member essentially or substantially remain axially stationary.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary side view of a jaw clutch according to the present invention,
shown mounted on a rotatable shaft and including a sprocket for rotatable engagement
with a chain, a representative link of which is illustrated;
FIG. 1
a is another side view of the jaw clutch, in partial cross-section;
FIG. 2 is a simplified schematic representation of the jaw clutch of FIG. 1,
showing opposing teeth of clutch plates of the clutch fully matingly engaged, a
clutch spring of the clutch in an initial or normal state for holding the clutch
plates together and a shock damper of the invention in a normal state;
FIG. 3 is another simplified schematic representation of the clutch of FIG.
1, showing the clutch plates urged axially apart by a disengagement force applied
between the opposing teeth thereof, the clutch spring compressed from the initial
state thereof, and the shock damper in its normal state;
FIG. 4 is another simplified schematic representation of the clutch of FIG.
1, showing the teeth of the clutch plates matingly disengaged to illustrate ratcheting
movement of one relative to the other, the clutch spring in a more compressed state,
and the shock damper in its normal state;
FIG. 5 is still another simplified schematic representation of the clutch of
FIG. 1, showing the teeth of the clutch plates partially matingly re-engaged during
the ratcheting, the clutch spring in a less compressed state, and the shock damper
in its normal state;
FIG. 6 is still another simplified schematic representation of the clutch of
FIG. 1, showing the opposing teeth more fully matingly engaged during the ratcheting
movement as a result of release of stored energy by the clutch spring, the clutch
spring again in its normal state, and the shock damper in a partially compressed
state for absorbing the energy;
FIG. 7 is a graphical representation of axial shock force over time for the
clutch of FIG. 1 without the shock damper of the invention;
FIG. 8 is a graphical representation of axial shock force over time for the
clutch of FIG. 1 with the shock damper of the invention;
FIG. 9 is an end view of the shock damper of FIG. 1; and
FIG. 10 is a sectional view of the shock damper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like numbers refer to like parts,
FIGS. 1 and 1
a show a jaw clutch
10 including a shock damper
12
constructed and operable according to the present invention in a system in cooperation
with the other components of the clutch for damping and dissipating axial force
loads resulting from rapid engagement of clutch
10 and ratcheting action
thereof under overrunning conditions. Jaw clutch
10 is of a common commercially
available type for transmitting power between two rotatable members, here including
an elongate rotatable shaft
14 and a rotatable sprocket
16, although
it should be understood that it is contemplated that the present invention has
utility for use with a wide variety of other rotatable members, including, but
not limited to, pulleys or sheaves, other shafts, rollers, and the like. Here,
sprocket
16 is partially encircled and rotated by a roller drive chain,
represented by a conventional chain link
18, rotated by a motor, engine,
or other drive means (not shown), in the conventional well known manner. Jaw clutch
10 is mounted on shaft
14 and is automatically operable under normal
conditions for connecting shaft
14 in rotatably driven relation to sprocket
16. Shaft
14 can be rotated for performing any useful function, such
as, but not limited to, rotating components within a feeder house
20 of
an agricultural combine, such as drive sprockets (not shown) of a feeder chain
arrangement (also not shown). In this regard, shaft
14 is supported in a
well known manner on feeder house
20 by a plurality of bearings, represented
by bearing
22 seated in a bearing housing
24 bolted or otherwise
suitably mounted on a side of feeder house
20 as shown. Feeder house
20
is representative of feeder houses used for conveying harvested crop from a header
of an agricultural combine to threshing apparatus thereof, and typically includes
several endless parallel chains spanned by slats which push or convey the crop
material upwardly along a bottom surface of the feeder house into an inlet region
of the threshing apparatus. From time to time, wads of crop material, brush, weeds,
and other items, may be conveyed through the feeder house so as to slow or stall
rotation of shaft
14. To avoid slowing or stalling rotation of the drive
chain or other components, as a result, and to avoid possible damaging torsional
stress on shaft
14 and other components, clutch
12 is automatically
disengageable to allow rotation of sprocket
16 relative to shaft
14
until the slowdown or stall condition is remedied or alleviated.
To achieve the above capability, clutch
10 includes a pair of clutch plates,
including a first clutch plate
26 and a second clutch plate
28. Clutch
plates
26 and
28 are disk shape members each having four axially
extending teeth
30 at equally angularly spaced locations around a rotational
axis
32. Clutch plates
26 and
28 are mirror images of each
other and are disposed such that teeth
30 thereof are axially opposing.
Opposing teeth
30 are matingly engageable as shown for joint rotation of
clutch plates
26 and
28 about a rotational axis
32 therethrough,
opposing teeth
30 being disengageable to allow relative rotation of clutch
plates
26 and
28 in the well known manner. First clutch plate
26
is supported about shaft
14 for rotation therewith and movement along an
axial path, denoted by arrow A, on a support
34 having an internally splined
hole therethrough which receives and is axially movable along an externally splined
portion of shaft
14 in the well known manner. Second clutch plate
28
is supported for joint rotation with sprocket
16 about axis
32 relative
to shaft
14, on a suitable rotatable member which is preferably a bushing
36 rotatable about shaft
14 at a fixed axial position therealong.
The axial position of bushing
36 can be fixed in any suitable conventional
manner, such as by abutment with a shoulder around shaft
14. Bushing
36
includes an annular shoulder
38 therearound at an axially fixed location,
and a backing washer
40 which axially abuts sprocket
16 opposite
second clutch plate
28.
Shock damper
12 of the present invention is preferably an annular disk
spring which extends around bushing
36 between shoulder
38 and backing
washer
40. Under normal operating conditions, shock damper
12 serves
as a substantially rigid member or spacer which, when opposing teeth
30
of clutch plates
26 and
28 are matingly engaged for joint rotation,
holds sprocket
16 and clutch plate
28 at a substantially stationary
axial position on shaft
14, as shown. On the opposite side of first clutch
plate
26, a resiliently yieldable clutch spring
42 is disposed about
shaft
14 between support
34 and a spring retainer
44. Retainer
44 is held in position on shaft
14 by a nut
46 threadedly
engaged with shaft
14 and tightenable for compressing clutch spring
42
to a desired extent for exerting a spring force, denoted by arrow FS, against support
34. Clutch spring
42 will have a spring rate sufficient to exert
a spring force FS of sufficient magnitude to urge first clutch plate
26
against second clutch plate
28, for holding opposing teeth
30 in
mating engagement for the joint rotation of clutch plates
26 and
28,
denoted by arrows B and C, such that shaft
14 connected to clutch plate
26 will be drivingly rotated by sprocket
16 connected to clutch plate
28, under anticipated normal load conditions. However, clutch spring
42
should allow clutch plate
26 to move away from clutch plate
28 to
allow ratcheting movement of opposing teeth
30 when a disengagement force
of a desired magnitude denoted by arrow FD (FIG. 3) in opposition to spring fore
FS, is exerted against the clutch plates, for instance, as a result of a high torque
condition resulting from opposition to rotation of clutch plate
26 such
as due to the conditions described above, namely, the presence of wads of crop
material, weeds, and other items in the feeder house, or other conditions, that
would slow or stall rotation of shaft
14 and/or potentially damage the rotating
components or cause other damage.
Thus, shock damper
12 of the present invention should be sufficiently
rigid so as to be capable of holding sprocket
16 and clutch plate
28
substantially stationary in the axial direction when anticipated routine spring
forces FS and disengagement forces FD are exerted thereagainst. Additionally, and
importantly, shock damper
12 should be resiliently yieldable under substantially
higher loads, so as to be capable of absorbing at least a substantial amount of
axial shock forces exerted against clutch plate
28 as a result of mating
reengagement of the teeth of the clutch plates during rapid ratcheting movement
thereof, and function as part of a system in cooperation with other components
of clutch
10 to dissipate the energy of the shock forces over a limited
or predictable time, while still holding clutch plate
28 and sprocket
16
substantially axially stationary, which for the purposes of the present invention
includes allowing only very limited axial movement thereof, such that operation
thereof is not impaired, and the potential for shock caused damage to components
carried on shaft
14, including sprocket
16, the chain, bearing
22,
and the chains in feeder house
20, is significantly reduced, compared to
if the resultant shock forces are not significantly damped. Such axial shock forces
for the present application for driving the chain drive of feeder house
20
have been measured to have a value of as much as 10,000 pounds. By limited axial
movement, what is meant is an amount of axial movement sufficiently small such
that impairment of the operation of, and damage to, the rotatable members will
not occur as a result of the movement. Here, this would mean an amount that would
include as a minimum the side play of the chain drive, which would be generally
be the difference between the maximum axial width D of the portion of the teeth
of sprocket
16 which engage the chain, and the inner axial width E between
the side bars of the narrower ones of links
18. This value would be likely
increased as a function of the distance between sprocket
16 and the next
closest other sprocket engaged with the chain, the longer the distance the greater
the value. Thus, for the present application the shock damper
12 should
have the ability to dampen the 10,000 pound shock force and dissipate the energy
thereof over a time interval or period less than that before the occurrence of
the next shock force as a result of ratcheting over another tooth. Because clutch
plates
26 and
28 each have 4 teeth at equally spaced locations therearound,
the time period between the occurrence of the shock forces will be equal to that
for the clutch plates to relatively rotate about ¼ revolution, which for the
normal operating speed of the present feeder drive application can be just a few
hundredths of a second, for instance, about 0.02 second.
FIG. 2 is a simplified schematic representation of jaw clutch
10 for
the present application, showing a disk spring shock force damper
12, shaft
14, sprocket
16 and clutch spring
42 which is a single compression
coil spring. Clutch spring
42 is shown at its normal or initial axial length
L
1. Shock force damper
12 is shown at its normal or initial axial
length L
2. Under normal or engaged conditions, clutch plates
26 and
28 are fully engaged by the exertion of spring force FS against support
34 with shock force damper
12 disposed in contact with backing washer
40 supporting sprocket
16 and second clutch plate
28, for
rotation of clutch plate
26 by clutch plate
28, as denoted by arrows
B and C. The axial height of opposing teeth
30 is also shown, as denoted
by dimension H. Here, H will have a value of about 0.25 inch. It should be noted
that adjacent ones of matingly engaged sets of teeth of clutch plates
26
and
28 are separated by spaces
48. Each set of the matingly engaged
teeth
30 have opposing ramp surfaces
50 in abutting relation and
through which the rotational driving force is transferred from the driving clutch
plate, here clutch plate
28, to the driven clutch plate, here clutch plate
26. Surfaces
50 are each preferably oriented at about a 50 to 60
degree angle to the direction of rotation denoted by arrows B and C, although it
should be understood that other angles for ramp surfaces
50, including perpendicular
to the rotational direction, and other height values H for teeth
30, can
be used, as required or desired for a particular application.
Referring also to FIG. 3, as discussed above, it is contemplated that from
time to time there will be instances, such as due to resistance to rotation of
the driven one of the rotatable members, when it will be desirable for the driving
one of the rotatable members, here sprocket
16, to be allowed to rotate
relative to the driven member, here shaft
14, such that potentially damaging
loads and stresses are not placed on the power transmission components, and such
that the other rotating members connected to the driving rotatable member are not
significantly slowed down. This is accomplished by allowing the rotatably driving
clutch plate, here clutch plate
28, to rotate in ratcheting relation to
the driven clutch plate, here clutch plate
26. This will occur when a disengagement
force denoted by arrow FD is generated between clutch plates
26 and
28
in opposition to, and greater in magnitude than, spring force FS exerted by clutch
spring
42, such that the clutch plates can be forced the distance H apart.
Because shock damper
12 is sufficiently rigid so as to at least substantially
retain its initial or original shape under spring force FS and disengagement force
FD, length L
2 thereof will remain substantially constant or be decreased
by only a small amount. As a result, clutch spring
42 will yield to the
disengagement force FD such that clutch plate
26 will be axially displaced
from clutch plate
28, denoted by arrow A, by an amount at least substantially
equal to the height H. Thus, the displacement of clutch spring
42 will be
equal to about L
1-H. As disengagement force FD overcomes spring force FS,
ramp surfaces
50 of the matingly engaged teeth
30 will slide one
relative to the other until axially opposing surfaces
52 of teeth
30
engage and hold the clutch plates
26 and
28 apart, as shown in FIG. 4.
Referring more particularly to FIG. 4, clutch
10 is shown with clutch
plates
26 and
28 held apart by sliding engagement of axially opposing
surfaces
52 of teeth
30 as clutch plate
28 and sprocket
16
rotate or ratchet jointly relative to clutch plate
26, as denoted by arrow
B. Clutch spring
42 is still displaced by the amount H and damper
12
is still at its initial length L
2. Opposing forces FS and FD are still present,
the energy thereof being stored as potential energy in spring
42.
In FIG. 5, teeth
30 of clutch plate
28 are shown rotated past teeth
30 of clutch plate
26 such that the clutch plates are no longer held
apart thereby. At this position, because teeth
30 of clutch plate
28
are rotating in the direction B relative to teeth
30 of clutch plate
26,
even if back surfaces
54 of opposing teeth
30 are briefly engaged,
little or none of disengagement force FD will be exerted therebetween to force
the clutch plates apart. Instead, the stored potential energy of spring
42
is suddenly released, as denoted by arrow PE, to drive clutch plate
26 rapidly
toward clutch plate
28, as denoted by arrow A.
Referring also to FIG. 6, the release of the potential energy PE to drive
clutch plate
26 toward clutch plate
28 will result in impact between
teeth
30 of the clutch plates with a resulting shock force, denoted by arrow
S
1, having a magnitude several times greater than that of both the spring
force FS and the disengagement force FD. When this impact occurs, clutch spring
42 will return to its initial length L
1, and the released energy
will be transferred through clutch plate
28 and backing washer
40
to shock damper
12 which will absorb at least a substantial portion of the
energy, while transferring some to shaft
14 as axial shock load S
2.
Absorption of the energy will cause shock damper
12 to be displaced or compressed
in the axial direction by an amount D, so as to have a resultant axial length equal
to L
2-D. Because shock damper
12 is a disk spring, when it absorbs
the energy and is resultantly deformed, some of the deformation will be in the
diameter and shape thereof in addition to in the length thereof, such that axial
displacement D and thus axial movement of clutch plate
28 and sprocket
16
can be minimized. Shock damper
12 will then release the absorbed energy
such that the energy will be at least partially dissipated by cooperative movements
of clutch spring
42 and clutch plates
26 and
28, and, as a
result the magnitude of shock forces or loads S
2 transferred to shaft
14
will be damped and much lower than the magnitude of the initial shock force S
1.
Thus shock force damper
12 and clutch spring
42 should be selected
so as to provide a desired torque transferring capability required for a particular
application while maintaining sprocket
16 at a substantially stationary
axial position on shaft
14, and such that shock damper
12 will absorb
a useful amount of the energy of anticipated shock forces, and further such that
shock force damper
12, clutch plates
26 and
28, and clutch
spring
42 will cooperate to dissipate a substantial portion of the shock
force energy to substantially lower the magnitude of resultant shock forces or
loads S
2 transferred to shaft
14.
As a preferred combination adapted for the present application, the spring rate
of the disk spring should be at least ten times greater than the spring rate of
the clutch spring. More preferably, the spring rate of the disk spring is at least
fifteen times greater than the spring rate of the clutch spring. A range of suitable
values for the spring rate of the disk spring can be between about 30,000 and about
40,000 pounds per inch and the spring rate of the clutch spring between about 2,000
and about 3,000 pounds per inch. More preferably, the spring rate of the disk spring
is between about 35,000 and 38,000 pounds per square inch and the spring rate of
the clutch spring is between about 2,100 and 2,400 pounds per square inch. More
specifically, a satisfactory spring rate of the disk spring is about 36,800 pounds
per inch and the spring rate for the clutch spring about 2,235 pounds per inch.
However, it should be recognized that other spring rates may be more suitable for
other applications, it being most important to recognize that the spring rate for
the shock damper should be sufficiently greater than that of the clutch spring
such that resultant shock forces exerted on the rotatable members will be damped
but significant movement of the second clutch plate will not be permitted.
Turning to FIG. 7, a graphical representation of resultant shock force measured
on shaft
14 versus time for ratcheting operation of jaw clutch
10
without shock force damper
12. Positive force measurements reflect forces
exerted in the direction to compress clutch spring
42 and negative force
values reflect shock forces resulting from release of stored energy. Thus, peak
56 reflects axial force on shaft
14 as disengagement force FD is
applied for matingly disengaging the teeth of clutch plates
26 and
28,
and negative peak
58 reflects the initial axial shock force exerted against
shaft
14 when the teeth are abruptly matingly re-engaged. The magnitude
of the disengagement force represented by peak
56 is about 2,000 pounds.
The magnitude of the shock force is about 10,000 pounds. Subsequent forces resulting
from the re-engagement have magnitudes of more than 6,000 pounds. This pattern
is repeated at about 0.02 second intervals.
FIG. 8 shows resultant axial shock forces exerted against shaft
14 with
shock force damper
12 installed on jaw clutch
10 as described above.
Here, the axial force exerted against shaft
14 by the disengagement force
FD still has a maximum value as denoted at peak
56 of about 2,000 pounds.
However, the maximum shock force exerted against shaft
14 is less than 4,000
pounds, as denoted by peak
16. This is also true of the subsequent ratcheting
actions at about the same time intervals as shown in FIG. 7 throughout a span of
about 0.10 second. Thus, it is apparent that resultant axial shock forces exerted
against shaft
14 are reduced by at least half, and by as much as 60% or
more. As a result of the substantially decreased axial shock forces exerted against
shaft
14, occurrence of resultant damage to components thereof is correspondingly reduced.
FIGS. 9 and 10 are an end view and a sectional view of shock force damper
12.
As noted above, shock force damper
12 is an annular disk spring having a
frusto-conical shape, including a larger diameter end
62 which is positioned
to abut and bear against backing washer
40, and an opposite smaller diameter
end
64 that is positioned in abutment with shoulder
38 of bushing
36, both as shown in FIG. 1. As also noted above, the disk spring of shock
force damper
12 will have a spring rate at least several times greater than
that of clutch spring
44, to provide the shock force damping capability
as graphically illustrated in FIG. 8. When shock force damper
12 absorbs
shock forces such as due to the release of potential energy PE, the disk spring
resiliently flattens in the axial direction and deforms in shape, the disk spring
having memory properties so as to return to its original shape after removal or
reduction of the force.
It will be understood that changes in the details, materials, steps, and arrangements
of parts which have been described and illustrated to explain the nature of the
invention will occur to and may be made by those skilled in the art upon a reading
of this disclosure within the principles and scope of the invention. The foregoing
description illustrates the preferred embodiment of the invention; however, concepts,
as based upon the description, may be employed in other embodiments without departing
from the scope of the invention. Accordingly, the following claims are intended
to protect the invention broadly as well as in the specific form shown.
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