Note: Descriptions are shown in the official language in which they were submitted.
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Title: "Clutchl'
An object of the invention is to provide a new and improved clutch.
According to the present invention we provide a clutch comprising a
pair of relatively rotatable and axially movable drive members, each having
torque transmitting abutments, a biasing means to bias the drive members
axially towards each other so as to be disengagabh/ connected in torque
transmitting relationship by a plurality of rotatable torque transmitting
elements interposed between the drive members and which are biased into
torque transmitting relationship with the torque transmitting abutments by
the biasing means when the clutch is engaged and which are movable out of
torque transmitting relationship with the torque transmitting abutments when
a relieving means relieves the biasing means and wherein the torque
transmitting elements are guided by a cage which is free to rotate relative to
both drive members during disengagement.
The clutch may be a torque limiting clutch and said movement of the
torque transmitting elements out of torque transmitting relationship may
occur when the torque exceeds a predetermined value and as a result of
movement of the drive members axially apart, the relieving means relieving
the biasing means when the torque exceeds the predetermined value.
When the torque to be transmitted exceeds the predetermined value the
torque transmitting elements commence to roll out of the torque
transmitting abutments and thus cause the drive members to be moved
axially apart, the relieving means then operates to relieve the biasing means
so that the drive members are spaced apart.
The cage may maintain the torque transmitting elements out of
engagement with the torque transmi-tting abutments of one drive member.
PreFerably the cage maintains the torque transmitting elements
adjacent the other drive member.
The other drive member may be provided with torque transmitting
element receiving means within which the torque transmitting elements are
received when the clutch is disengaged and the torque transmitting elements
being maintained within the receiving means by the cage.
The receiving means may be provided by the torque transmitting
abutments of the other drive member.
The one drive member may be axially stationary relative to a body part
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of the clutch and the other drive member axially movable relative to the
body part under the influence of the biasing rneans.
Alternatively, the one drive member may be axially movable relative to
a body part of the clutch under the influence of ~he biasing means and the
other drive member may be axially stationary relative to the body part.
Means may be provided to limit movement of the cage in a direction
away from the other drive member.
The cage may be biased towards the other drive member by a cage
biasing means
Further alternatively, the cage may be biased towards the other drive
member by a cage biasing means and, in addition, means may be provided to
limit movement of the cage in a direction away from the other drive
member.
Said means to limit movement of the cage may comprise abuiment
means to abut an inner annular surface portion of the cage or to engage an
outer annular surface portion of the cage.
The cage biasing means may comprise spring biasing means such as a
plurality of coil compression springs disposed angularly around the axis o-F
rotation of the clutch, and may act between the one drive member and the
cage.
Antifriction bearing means may be provided between at least one of the
; cage, cage biasing means and the one drive member.
- The bearing means may be provided between the cage and the cage
biasing means.
The bearing means may comprise a sliding bearing comprising a
generally annular track provided on the cage and a bearing member engaged
by the biasing means.
One bearing surface may be provided by a PTFE surface and the other
by a steel or other soitable bearing material.
The cage biasing means may act between the cage and a member
axially fixed and rotatable relative to the one drive member and may be
disposed radiGlly inwardly of the one drive member.
The one drive member may be rotatably and non~axially moveably
mounted relative to a hub member, the other drive member being non-
rotatably and axially moveably mounted relative to said hub member and the
biasing means being static and the hub member being rotatable relative to
the biasing means.
3 1 3~ ~3~
The other clutch member may be rotatably and non-axially moveably
mounted relative to a hub member, the one drive member being non-rotatably
and axially moveably mounted relative to said hub member and the biasing
means being static and the hub member being rotatable relative to the
biasing means.
The cage biasing means may act between the hub member, or an
element fixed relative thereto, and the cage.
The cage biasing means may act between the inner member of a bearing
carried on the hub member and the outer member of which rotatably mounts
the one drive member on the hub member.
The cage may be provided with apertures wi thin which the torque
transmitting elements are received and be of a thickness to permit o-f the
torque transmitting elements projecting from opposite sides oF the cage for
engagement with -the torque transmitting abutments of the drive members.
The cage may be provided with means to retain the torque transmitting
elements from movement through the apertures in a direction away from the
other drive member.
Said means may comprise a generally frusto-conical configuration of
each aperture.
The cage may be thinner than the radius of the torque transmitting
element. This is particularly so when the torque transmitting abutments have
a relatively steep abutment surface. For example, a surface inclined at
about 55 or more to a plane normal to the axis of rotation of the clutch.
The cage may be movable axially relative to each drive member so that
on disengagement of the clutch when the torque transmitting elements roll
out of engagement with the abutments and move the drive members apart the
cage is moved away from the other drive member.
The cage biasing means may serve to bias the one drive member away
from the other drive member when the clutch is disengaged.
The cage biasing means may comprise an element which has a cage
abutment means and an other drive member abutment means spaced so that
the other drive member abutment means can abut the other drive member
when the clutch is disenqaged and the torque transmitting elements are
receiving within torque transmitting element receiving means with which the
other drive member is provided.
Alternatively, further biasing means may be provided to bias the one
and other drive members apart.
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The further biasing means may act between the one drive member and a
part preven-ted at least from movement relative to the other drive member in
a direction away from the one drive member.
The further biasing means may comprise spring biasing means such as a
plurality of coil compression springs disposed angulariy arourid the axis of
rotation of the clutch.
The cage or furt~er biasing means may comprise a ring member
concentrically disposed relative to the cage.
The ring member may be constrained from rotation relative to the hub
by at least one guide element non-rotatably associated with the hub and
permitting of axial movement of the ring mernber relative to the hub.
The ring member may be constrained from rotation relative to the hob
by an annular member fixed relative to the hub and a plurality of pins
extending between the annular member and the ring member, the pins being
non-rotatably connected to the annular and ring members and being slidable
relative to at least one member thereof.
A coil compression spring may be disposed around at least one of said
pins to bias the ring and annular members apart.
The biasing means may comprise a fluid pressure biasing means such as
a pneumatic biasing means.
Movement of the one drive member away from the other drive member
may cause operation of the relieving means.
The relieving means may operate to release the fluid pressure.
The torque transmitting abutments may be disposed equally radially and
angularly relative to the axis of rotation of the drive members.
In this case each torque transmitting element may be received in a
circumferentially adjacent torque transmitting abutment to the torque
-transmitting abutment with which it was engaged prior to disenaagement.
Alternatively, the torque transmitting abutment may be disposed at
different radii and/or angular positions relative to the axis of rotation of thedrive members.
In this case each torque transmitting element may be received only in
the torque transmitting abutment with which it was engaged prior to
disengagement.
Guide means may be provided to constrain radi~l movement of the cage
and the guide means may comprise an outwardly facing surface portion to
engage an inner circumferentially extending surface portion of the cage or an
inwardly facing s~lrface portion to engage an outer circumferentially
extending surface portion of the cage.
s ~ 131~ ~ 3~
A first of said drive members may be rotatably and non-axially
moveably mounted relative to a hub member, the second of said drive
members being non-rotatably and axially moveably mounted relative to said
hub member, the biasing means being stqtic and the hub member being
rotatable relative to the biasing means and to a static member, the static
member having said first drive member rotatably mounted thereon.
The relieving meqns may comprise a valve means operable to relieve
fluid pressure as a result of relative movement of the drive members on
disengagement of the clutch.
The biasing means may compr ise at least one piston moveable in a
cylinder and the valve means comprise a valve member co-operating with a
valve seat and the valve member being engaged by a piston to move the valve
member out of sealing engagement with the valve seat to relieve the fluid
pressure.
Means may be provided to interrupt the supply of fluid pressure to the
biasing means and disengagement of the clutch.
According to another aspect of the present invention we provide a
clutch comprising a pair of relatively rotatable drive members, each having
torque transmitting abutments, disengagably connected in torque transmitt-
ing relationship by a plurality of rotatable torque transmitting elements,
there being a plurality of circumferentially disposed, fluid operated, biasing
means to bias said elements into torque transmitting reiationship with said
members when the clutch is engaged and to permit of disengagement of the
torque transmitting elements when a relieving means relieves the bias.
The clutch may be a torque limiting clutch and said movement of the
transmitting elements out of torque transmitting relationship may occur
when the torque exceeds a predetermined value and the relieving means may
relieve the biasing pressure when the torque exceeds the predetermined
va lue.
A clutch according to the second aspect of the invention may
incorporate the first aspect of the invention or any o-f the preferred features
mentioned in connection with the first aspect of the invention which are
applicable to a clutch according to the second aspect of the invention.
The invention will now be described by way of example with reference
to the accompanying drawings wherein;
Figure I is a longitudinal cross-sectional view through a torque limiting
clutch embodying the invention7
Figures 2 to 8 are9 respectively, part longitudinal cross-sectional views
through seven different alternative embodiments of the invention,
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Figure 9 is a longitudinal cross-sectional view through an eighth
alternative embodiment of the invention,
Figure 9a is a fragmentary longitudinal cross-sectional view showing a
modification of the embodiment of Figure 9.
Figure I û is a longitudinal cross-sectional view through a ninth
alternative embodiment of the invention, and
Figure 11 is a part longitudinal cross-sectional view of a modification
applicable to all the previously mentioned embodiments.
Referring to Figure 1, there is illustrated a torque limiting clutch C
comprising drive members 10, Il. In this example the member lû will be
described as a driving member and the member 11 as a driven member but it
should be understood that if desired the member 11 may be the driving
member and the member 10 would then be the driven member.
The driving member 10 comprises in this example a drive gear 12 driven
by a pinion from a prime mover (not shown) in a conventional manner. The
driving member 10 may, alternatively, be driven in any desired manner. The
gear 12 is fastened by set screws 13 and roll pins 14 to a body 15 which is
connected by bolts 16 and roll pins 17 to a driving plate 18 of the clutch.
Rotatably mounted within the body 15 by means of a pair of ball bearings 19
is the driven member I Iwhich can be connected to an apparatus to be driven
in any desired manner.
The driven member 11 has a driven clutch plate 2û splined thereto as
shown at S for axial sliding and non-rotatable movement relative to the
driven member 11. Interposed between the driving and driven clutch plates
18, 20 is a cage plate 21 which has a plurality of apertures 22 for torque
transmitting elements in the form of balls 23. The apertures 22 are of
frusto-conical configuration having their smaller diameter end adjacent the
driven clutch plqte 20 and their larger diameter end adjacent the driving
clutch plate 18.
The thickness of the cage plate 21 relative to the diameter of the balls
23 is such that the smaller diameter end o-f the frusto-conical aperture 22
engages the balls 23 as shown when the clutch is engaged i.e. on a chord
approximately mid-way between the centre of the ball and its surface. The
driving and driven clutch plates 18, 20 are provided with toraue transmitting
abutments 24, 25 respectively which are in the form of generally
frusto-conical recesses having an included angle of approximately 70. If
desired other angles may be used, for example 9û, but a smaller angle such
as 7û is preferred because this perrnits of transmittal of q greater toraue
between the clutch plates for a given force biasing the plates together by a
`` ~31~3~
-- 7 -
resilient biasing meqns 30.
If desired the abutment may be of other shape such as generally prism
shaped and again the abutment surfaces would be similarly inciined. That is
the included angle could be 70 or 90 and hence would be inclined at 55 or
45 respective to a plane normal to the axis of rotation X-X of the clutch C.
The resilient biasing means 30, in the present exarnple, comprises a
ball bearing 31 the inner race 32 of which is engaged by the driven clutch
plate 20 and the outer race 33 of which s engaged by a plurality of pistons 34
slidable in a corresponding plurality of cylinders 35 which are carried on the
outer race 36 of a second ball bearing 37 the inner race 38 of which is
engaged with the driven clutch member 11. An O ring seal R is provided
between each pistor~ 34 and its associated cylinder 35. In the present
example four pistons 34 and associated cylinders 35 are provided
circumferen-tially spaced around the clutch at the equi-angular positions. A
different number of pistons may be provided, for example, eight. If desired,
if a user wishes the clutch to transmit a very low torque then one or more of
the piston and cylinder arrangements may be blanked off. Alternatively, if
desired, instead of a plurality of circumferentially spaced piston and cylinder
arrangements a single annular piston and cylinder arrangement may be
provided.
Air if fed from a source of air under pressure via a passageway 39 to
each cylinder 35 so that when air is applied under pressure to the interior of
the cylinder 35 the associated pistons 34 are biased to the right in the figure
to bias the driven clutch plate 2û towards the driving clutch plate 18 and thus
to force the balls 23 into torque transmitting relationship with the abutments
24, 25 on the plates 18, 20 respectively. If desired any other form of
relievable resilient biasing means may be provided.
A cage biasing means comprises a plurality of coil compression springs
40 provided at equi-angularly disposed positions around the axis X-X in
stepped passages 41 provided in the driven clutch plate 20. A plurality of
pins 42 are received within the passages 41 and are surrounded by the coil
compression springs 40. The pins 42 project from an annular steel pressure
ring or washer 43 and the coil compression springs 40 are engaged between
the washer 43 and the step in the passages 41 so that the washer 43 is biased,
in Figure I, to the right against a PTFE washer 44 provided in a recess 45 of
annular configuration in the cage plate 21.
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A split ring 4~ is located in a groove 47 of the driven member 11 and
provides an outwardly facing surface part 48 for engagement with an
inwardly facing surface part 49 of the cage so as to restrain the cage from
movement radial to the axis X-X when the clutch is disengaged as
hereinafter described. The split ring 46 is retained in the groove 47 by a
circlip or the like 50 which can abut an annular portion 51 of the cage plate
21 over which the PTFE washer may extend if desired and as shown.
In use, when the driving member 1û is rotated then so long as the torque
to be transmitted to the driven clutch member 11 is lower than a
predetermined torque, torque is transmitted between the clutch members by
the balls 23 and torque transmitting abutments 24, 25. When the torque to be
transmitted reaches a predetermined torque the balls 23 begin to roll out of
the associated abutments 24, 25 when the force applied by the pistons 34 is
less than the resultant force tending to bias the driven plate 20 to the left inthe Figure.
As the driven plate 2û moves away from the driving plate 18 the piston
34 is pushed to the left in the figure and this causes a relieving means
actuating disc 52 to engage a sensor of a relieving means operating means 53
such as a micro-switch to open a electrically operated valve in the supply of
air to the passages 39 so that the air supply is cut off and the pressure withinthe cylinders 35 released thereby relieving the resilient bias of the driven
plate 20 to the right in Figure 1.
In addition, as the balls 23 ride out of their associated abutments 24, 25
they rotate and cause the cqge plate 21 to rotate at half the relative speed
between the driving and driven clutch plates, relative to each clutch plate.
Because of the above described frusto-conical configuration of the apertures
22 and their relationship with the size of balls 23 the cage plate 21 is also
moved to the left in the figure away from the driving clutch plate 18~
When the pressure in the cylinders 35 is relieved as described
hereinbefore the coil springs 4û bias the driven clutch plate 20 to the left in
the figure until the biasing force of the springs 4û is reduced to an extent
that it cannot overcome the friction in the splined connection S and seals R.
As the driving and driven members continue to rotate relative to one
another the balls 23 continue to rotate until they become circumferentially
aligned with the next adjacent torque transmitting abutments 24? 25 in the
driving and driven clutch plates. When the balls are thus aligned the springs
4û urge the cage plate 21 to the right which movement is permitted by the
9 131~3~
alignment of the balls 23 with the torque transmitting abutments 2~ in the
driving clutch plate 18 and thos the cage plate guides the balls 23 into the
abutments and maintains the balls therein whilst the driving clutch plate 18
continues to rotate relative to the driven clutch plate 20. The cage plate 21
thus maintains the balls 23 out of position for engagement with the
abutments 25 of the driven ctutch plate 20 so that relative rotation between
the driving and driven clutch plates can continue without any risk of the balls
chattering as a result of engagement with the qbutments 25. The PTFE ring
44 running against the steel ring 43 has been found to provide a satisfactory
bearing because the spring force required to be applied by the springs 40 is
relatively light. If desired, however, any other suitable bearing means may
be provided such a sliding bearing comprising other suitable materials or a
rolling bearing such as a needle race.
It may be that in operation depending upon the particular
circumstances, such as the speed of rotation of the clutch and the torque to
be transmitted, the balls 23 do not enter the next adjacent torque
transmitting abutments as described above. For example, particularly at high
speeds of revolution the inertia may be such that the balls 23 bounce over one
or more of the sequentially adjacent torque transmitting abutments 24 before
the cage plate 21 can maintain the balls 23 in engagement with the torque
transmitting abutments 24. In practice this will occur only in a small number
of applications and is of no consequence since no significant damage will be
done by this limited amount of bouncing. Conversely, in some circumstances
the balls 23 may slip during disengagement of the clutch so that the cage
plate 21 does not rotate sufficently relative to the driving plate 18 for the
balls 23 to be initially aligned with the torque transmitting abutments 24. In
this case friction will cause the cage subsequently to rotate and bring the
balls 23 into alignment with the abutments 24.
In certain circumstances and where the separation between the driving
and driven plates is sufficiently great the balls 23 may be maintained aut of
engagement with the recesses of one clutch plate even though they are not
received in any receiving means of the other clutch plate.
Particularly at high speeds of revolution the driven clutch plate 20 and
the cage plate 21 may be moved away from the driving clutch plate 18 at
relatively high speed that the resulting momentum may cause the cage plate
21 to be positioned sufficiently closely adjacent the driven plate 2û for the
balls 23 to at least partially enter the torque transmitting abutments 25
: .. ~ .. ...
Io 131~13~
thereof before the coil springs 40 of the cqge biasing means can move the
cage plate 21 away from the driven clutch plate 2û. Accordingly, it is
preferred to provide a means to limit movement of the cage in a direction
away from the driving plate t8 and in the present embodiment this is
provided by the circlip 50 which abuts the annular portion Sl of the cage
plate 21 to limit movement of the cage plate 21 to the left In Figure I whilst
the driven plate 20 can continue to move to the left. If desired, this rneans
to limit movement of the cage in a direction awuy from one drive member
may be omitted where the circumstances of services permit of this, for
example, when the clutch is used at a relative low speed of rotation.
If desired any other form o-f cage biasing means to bias the cage plate
towards the driving plate 18 which reacts against the driven clutch plate 20
may be provided.
Where, as in the present example and as is preferred, the torque
transmitting recesses 24, 25 have an included angle of 7û the space available
between the clutch plates 18, 20 for the drive plate is relatively small and
hence the thickness of the cage plate is less than half the ball diameter. It isfor this reason that the cage plate is arranged to be movable axially with the
balls as they move out of the recesses in the driving clutch member.
Thc predetermined torque at which the clutch disengages can be easily
adjusted by varying the pressure of the air acting on the pistons 34. The air
pressure and hence the torque level can be easily adjusted whilst the clutch is
running it being appreciated that, of course, the cylinders 35, pistons 34, disc50 and a dust shield 54 are stationary qt all times and thus there is no
problem ir- feeding air to the passages 39 operating the relieving means.
The relieving means may be arranged to relieve the biasing means when
~he driven clutch plate 2û has moved through a axial distance somewhat less
than that reauired to completely disengage the balls 23 from the recesses 24
and 25 but complete disengagement is achieved by the hereinhefore described
springs 40 when the biasing means is relieved.
The number of torque transmitting balls and abutments are chosen
according to the torque to be transmitted and, for example, may comprise
six balls and associated pairs of recesses.
The means for relieving the biasing means may comprise a suitable
means for example any suitable means sensitive to movement of ony
convenient part which moves with the driven clutch plate 20.
i
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316~31
In a modification the torque transmitting elernents 23 and associated
torque transmitting abutments 24, 25 are disposed at different radii and/or
angular positions relative to the axis of rotation X-X of the clutch. For
example, at least one ball 23 and its associated torque transmitting
abutments may be disposed as shown at 23a in dotted line whilst at least one
other ball 23 and its associated torque transmitting abutments is disposed as
shown in full line in the Figure. lhis ensures that the clutch can only be
engaged when the drive members are in a unique angular relationship.
In such a arrangement the driving and driven clutch members lû, 11
must rotate through two revolutions relative to each other to rotate the cage
through one complete revolution so that the balls 23 are in position to
occupy, receiving means provided by the same recesses 24~ 25 they occupied
prior to disengagement. This increases the time interval between the start of
disengagement and the positioning of the balls 23 in position for entering the
receiving means compared with the time interval which obtains in the first
described embodiment where it is necessary only for the clutch parts to
rotate sufficiently to move the balls into position for engagement in the next
adjacent torque transmitting abutments to those occupied prior to
disengagement. Thus, a longer period is provided for the relieving means to
relieve the air pressure which is particularly advantagous at high speeds of
revolution. This modification can be applied to all the other embodiments
described hereinafter.
Referring now to Figures 2 to lû these illustrate nine further different
embodiments which are the same as the embodiments described hereinbefore
with reference to Figure I except for the features shown differently in the
drawings and hereinafter to be described. The same reference numerals have
been used in Figures 2 to I û as were used in Figure I to refer to
corresponding parts.
In the embodiment shown in Figure 2 the split ring 46 and circlip 50 are
omitted and instead the cage plate 21 is constrained from radial movement
relative to the axis X-X by means of a cylindrical sleeve 2ûO fixed by screws
201 to the driving clutch plate 1~. The sleeve 20û provides an inwardly
facing circumferentially extending surface part 2û2 For engagement with an
outwardly facing circumferentially extending part 203 of the cage 21. The
sleeve 2ûO has an inturned flange 204 for engagement with an unnular surface
part 205 of the cage 21 and has the same effect as the circlip 50 described
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- 1 2 ~ 1 3 1
hereinbefore. In all other respects the embodiment illustrated in Figure 2 is
as previously described.
In a modification of the embodiment illustrated in Figure 2 the springs
4û and associated components 41-44 may be omitted. In this case there
would be no biasing of the cage 21 towards the driving clutch plate 18 and
satisfactory operation of the clutch would be dependent upon the driven
clutch plate 20 being moved sufficiently far to the left to unload the torque
transmitting balls 21 with movement of the cage 21 to the left being limited
by the flange 2û4.
Such an alternative is not preferred but may prove satisfactory in
certain operating conditions particulorly at slow speeds of rotation of the
clutch. A conceptually similar modlfication may be macle to the embodiment
illustrated in Figure I in that the springs 4û and associated components 41-44
may be omitted. The split ring 46 and circlip Sû would serve to limit
movement of the cage plate 21 away from the driven plate 18 and thus the
clutch would operate in the same manner as the modificGtion of the version
shown in Figure 2 without a cage biasing means described hereinbefore.
Referring now to Figure 3, in this embodiment a cage biasing means is
provided by springs 4û, passage 41, which in the present example is not
stepped but closed by a suitable closure member 30û, pins 42, steel ~Nasher
43 and PTFE washer 44. The cage biasing means acts between the driving
clutch plate 18 and the cage plate 21. In addition, the frusto-conical
aperture 22 is orientated in the reverse direction so that the smaller
diameter end thereof is adjacent the driving clutch plate 18. A split ring 46
is again provided and is located in a groove 47 in the driven clutch member 11
by a circlip or the like 5û but which in this example is provided on the side ofthe clutch plate 21 adjacent the driving clutch plate 18. In use, the clutch
operates essentially as described hereinbefore in connection with Figure I
except that the cage biasing means 40-44 serves to bias the cage towards the
driven clutch plate 20 so that the balls 23 are maintained in receiving means
such as torque transmitting abutments 25 provided in the driven clutch plate
20 and the driven clutch plate 20 and cage plate 21, when the clutch has fully
disengaged, rotate together relative to the driving clutch plate 18. The cage
biasing means ~0-44, in this embodiment, not only bias the cage plate 21
away frorn the driving clutch plate 18 but also bias the driven clutch plate 20
away from the driving clutch plate 18 through the intermediary of the cage
plate 21 and apertures 22 and balls 23.
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Referring now to Figure l~. This embodirnent is essentially the similar
to that described with reference to Figure 3 but radial location of the cage
plate 21 is provided by a cylindrical sleeve 400 fastened by screws 401 to the
driven clutch plate 20. The sleeve 400 has an inturned flange 402 which is
engagable with an annular surface part 4û3 of the cage pla~e 21. The split
ring 43 and circlip 50 of the Figure 3 embodiment are omitted. This
embodiment operates in the same way as described hereinbefore with
reference to Figure 3 except that there is a positive limit to movement of
the cage plate 21 away from the driven clutch plate 2û by virtue of the
flange 4û2. Thus, if, as a result oF n1omentum and inertia on disengagement,
particularly at high speeds, there is any tendency for the clutch plate 21 to
move away from the driven clutch plate 20 and remain adjacent the driving
clutch plate 18 then the engagement between the flange 402 and annular
surface part 403 wi11 provide a positive limit to such separation of the cage
plate 21 from the driven plate 2û.
In a modification, not preferred3 but which may be suitable in certain
applications particularly at low speeds of operation the cage biasing means
provided by the components 4û-44 may be omitted and operation of the
clutch rely on the clutch plate movement limiting means provided by the
flange 4û2 and annular surface 403 in a similar manner to the corresponding
modification of the embodiment described with reference to Figure 2.
Referring now to Figure 5. In this embodiment the cage biasing means
comprising the components 40-44 described hereinbefore is provided in a
similar manner to the embodiment described with reference to Figure I
except that these components are provided at a position which is radially
outwardly of the position at which they are provided in Figure 1. Inwardly of
the cage biasing means is provided a further biasing means comprising a
plurality of coil compression springs 500 provided at equi-angular positions
around the axis X-X in stepped passages 501 provided in the driven clutch
plate 20. A plurality of pins 502 are received within the passages 501 and are
surrounded by the coil compresion springs 500. The pins 502 project from an
annular steel ring 503 and the coil compression springs are engaged between
the ring 503 and the step in the passages 501 so that the clutch plate 20 is
biased, in Figure 5, to the left away from the driving clutch plate 18. The
ring 503 is mounted on the outer edges of the splines S of the driven clutch
member 11 and has an annular end surface 504 which abuts an annular surface
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part SOS of the driving clutch plate 18. The ring 503 is prevented from
movement away from the driving clutch plate 18 by a circlip 506. The ring
Sû3 and clutch plate 21 have mutually co-operating rebates which provide a
space 507 to permit of movement of the clutch piate 21 cway from the
driving clutch plate 18 during disengagement of the clutch.
In this embodiment instead of relying on the cage biasing means 4û-44
both to bias the cage 21 towards the driving clutch plate 18 and to bias the
driven clutch plate 2û away from the driving clutch plate 18 the further
biasing means Sûû-Sû7 is provided to supplement the bias of the driven clutch
plate 2û away From the driving clutch plate 18. The springs llû and Sûû may
be chosen of appropriate strength for their purpose.
The rebate in the ring 503 provides an outwardly facing circumferential
surface Sû8 which cooperates with an lnwardly facing circumferential surface
part 509 of the cage plate 21 to guide the cage plate 21 radially relative to
the axis X-X of the clutch.
Referring now to Figure 6. This illustrates a modification of the
embodiment described with reference to Figure S. In this modification radial
location of the clutch plate 21 is provided by a cylindrical sleeve 600 secured
by screws 6ûl to the driving clutch plate 18. The inner periphery of the
clutch plate 21 does not engage any locating member and the ring 503
described hereinbefore is formed in two separate parts namely, a part marked
603 in Figure 6 and a separate member in the form of a split ring 6û4 secured
in a groove ~7 in the driven clutch member 11 by a circlip 50.
The sleeve 60û has an inturned fiange 605 which engages an annular
surface part 606 which limits movement of the clutch plate 21 away from the
driving clutch plate 18 in a manner similar to that described hereinbefore in
connection with Figure 2.
Referring now to Figure 7. In this embodiment there is no cage biasing
means but instead a cage limiting means comprising a sleeve 700 secured by
screws 7ûl to the driven clutch plate 20 and having an inturned flange 702 for
engagement with an annular surface part 7û3 of the cage plate 21. In this
embodiment the frusto-conical apertures 22 in the cage plate 21 have their
smaller diameter ends adjacent the driving clutch plate 18.
A further biasing means is provided between the driving clutch plate 18
and the driven clutch plate 20 and comprises a plurality of coil compression
springs 70~ disposed equi-angularly about the axis X-X of the clutch in
passages 705 which are closed by a closure member 706. A plurality of pins
- 15 - ~ 3 1
707 are received within the passages 705 and are sorrounded by the springs
704. The pins 707 project frorn an annular steel pressure ring or washer 708
and the coil compression springs 704 are engaged between the washer 708 and
the closure member 706 so that the washer 708 is biased, in Figure 7, to the
left against a PTFE washer 709 provided in a recess 71 û of annular
configuration in the driving clutch plate 20.
In use, on disengagement of the clutch, the further biasing means
704-710 biases the driven clutch plate 20 away from the driving clutch plate
18 to ensure that the balls 23 are maintained out of engqgement with the
torque transmitting recesses 24 in the driving clutch plate 18 as a result of
the clutch plate 21 being moved to the left by the flange 702 as a result of
movement of the driven clutch plate 20 to the left both by the act of
disengaging the clutch and the effect of the further biasing means 704-171û.
Referring now to Figure 8 there is provided a cage biasing means
comprising coil compression springs 800 and pins 801 received in a stepped
bore 8û2 and acting to urae a washer or pressure ring %û3 against PTFE
washer 804 essentially disposed as described in connection with previous
embodiments. The cage plate 21 is arranged with the smaller diameter end
of the frusto-conical apertures 22 adjacent the driving clutch plate 18 and
the driven clutch plate 20 has a sleeve 805 which guides the cage plate 21
radially and has an inturned flange 806 for engagement with an annular
surface part 807 of the cage plate 21. In addition, a further biasing means is
provided comprising a plurality of coil compression springs 808 and pins 809
engaged in bores 810 closed by closure member 811 and which serve to urge a
washer or pressure ring %12 against a PTFE washer 813 received in a rebate
814 in the driven clutch plate 20, all as described hereinbefore in connection
with Figure 7. In this embodiment the cage biasing means 800-804
resiliently biases the cage 21 towards the driven clutch plate 20 to maintain
the balls 23 within receiving means such as provided by torque transmitting
abutments 25 in the driven clutch plate 20. The flange 806 provides a
positive limit to movement of cage 21 away from the driven clutch plate 20
which is particularly suitable when the clutch is used in an application where
it rotates at high speed to avoid any risk of the cage plate 21 moving
adjacent the driving clutch plate 18 so that the balls 23 can engage the
abutments 24 thereof before the cage biasing means 800-804 can move the
cage plate 21 away from the driving clutch plate 1%~ If desired, in a
modificationS the flange %06 may be omitted.
- 16- 13~13~
Referring now to Figure 9, the driving member 10 is as described in
connection with Figure 1, except that the drive gear 12 and the methods of
attachment, which are the same as in Figure 1, are not illustrated.
The body 15 in the present example is machined so as to have formed
integral therewith a part 918 corresponding to the driving plate 18. The cage
plate 21 has apertures 922 which are generally cylindrical but have a smaller
diameter end portion adjacent to the driving clutch plate 918. As in the case
of previous embodiments the thickness of the cage plate 21 relative to the
diameter of the balls 23 is such that the smaller diameter end of the aperture
922 engage the balls 23 as shown when the clutch is engqged, i.e. on a chord
approximately mid-way between the centre of the ball and its surface.
The main difference compared with the previously described
embodiments, lies in the cage biasing means which, in the present example,
avoids sliding between the parts of the biasing means when the clutch is
running free after the clutch is disengaged.
To this end the cage biasing means comprises coil compression springs
940 provided, at equally angularly disposed positions around the axis X-X, in
stepped passages 941 provided in an annular member 96û fixed relative to the
driven member 11. The springs are guided by pins 942 which are disposed
within the passages 941 so that their right-hand ends, in Figure 9, are slidablewithin the smaller diameter part of the associated passage 941. At their
other ends the pins 942 are fixed to a further annular ring member 961 which
is rotatable and slidable relative to the cage plate 21. A clearance is
provided between opposed cylindrical surfaces of the ring member 961 and
the cage plate 21 so as to permit of free relative rotation and longitudinal
sliding movement therebetween whilst an internal cylindrical surface of the
ring member 961 is a clearance fit on the splines S so that the ring member
961 is guided for axial sliding movement by the splines S.
If desired, alternative guiding arrangements may be provided. For
exan ple, the cage plate 21 may be guided for rotation and sliding relative to
the driven member i I by a guide surface engageable with an external
cylindrical surface 21a of the cage plate 21; for example, a guide surface
provided on a sleeve 9ûO of the driving clutch plate 918 or by a similar
surface associated with the driven clutch plate 20, in this case the clearance
between the ring member 961 and the cage plate 21 may be such that it is the
cage member which guides the ring member 961 for such movement whilst
the clearance between the ring member and the splines is greater.
17 ~ 3 ~.
Alternatively, a combination of the above arrangemen~s may be provided so
that both the splines S and the cage plate 21 share the guiding function.
Further alternatively, the ring member 961 rnay be guided by the pins 942
alone or in combination with any of the previously described arrangements, or
the ring member 961 may be guided by the pins 942 alone or together with
the splines S and the clearance between the ring member 961 and the cage
plate 21 being such that the cage plate is guided by the ring member for said
rotation and sliding.
The ring member 961 has an end surface 961a and a shoulder 961b which
are spaced apart by a distance greater than the thickness of a part of the
cage plate 21 therebetween. The coil compression springs 940 are engaged
between the further annular member 961 and a shoulder between the larger
and smaller diameter parts of their associated passage 941.
In use, when the torque to be transmitted reaches a predetermined
torque, the balls 23 begin to roll out of the associated abutments 24, 25 when
the force supplied by the pistons 34 is less than the resultant force tending tobias the driven plate 2û to the left of Figure 9. As the driven plate 20 moves
away from the driving plate 18 the piston 34 is pushed to the left in Figure 9
to operate the relieving means as described in connection with Figure 1.
In addition, as the balls 23 ride out of their associated abutments 24, 25
they rotate and cause the cage plate 21 to rotate at half the relative speed
between the driving and driven clutch plates, relative to each clutch plate.
In addition~ the springs 940 bias the cage plate 21 to the left in Figure 9 so
that it follows the axial movement of the balls 23.
As the driving and driven members continue to rotate relative to one
another, the balls 23 continue to rotate until they become circumferentially
aligned with the next adjacent torque transmitting abutments 249 25 in the
driving and driven clutch plates. 1Nhen the balls are thus aligned, the springs
940 urge the cage plate 21 to the left, which movement is permitted by the
alignment of the balls 23 with the torque transmitting abutments 25 in the
driven clutch plate 2û and thus the cage plate 21 guides the balls 23 into the
abutments and maintains the balls therein, whilst the driving clutch plate 18
continues ~o rotate relative to the driven clutch plate 20. When the balls 23
are engaged in the next adjacent abutments 25, the end surface 961a of the
ring 961 engages the driven clutch plate 20 and the driven clutch plate 2û is
thus biased to the left in Figure 9 until the biasing force of the springs 94û is
redvced to an extent that they cannot overcome the friction in the splined
-
- 18- 13~6~3~
connection S and seals R. The shoulder 961b prevents movement of the cage
plate 21 to the right away from the driven plate 20 and hence the balls 23 are
maintained at least partially engaged within the abutments 25.
The cage plate 21 thus maintains the balls 23 out of position for
engagement with the abutments 24 of the driving clutch plate 18 so that
relative rotation between the driving and driven clutch plates can continue
without any risk of the balls chattering as a result of engagement with the
abutments 24. Because the springs 94û are fixed relative to the driven
member I 1, they, and the ring 961, are fixed relative to the driven clutch
plate 20 and so there is no relative rotation at any time between any of the
parts of the biasing means. In particular, there is no relative rotation
between the driven clutch plate 2û and the surface 961b of the ring member
961 which acts thereon. There is, of course, relative rotation between the
shoulder 961 b and the cage plate 21 but this occurs only during
disengagement and so the contact is for q very limited period of time and the
extent of rotational movement is very limited, so that no special anti-friction
bearing means is required between the shoulder 961b and the cage plate 21,
although, of course, an anti-friction bearing means could be provided if
desired.
The above described sequence of operations assumes that there is
sufficient delay in the air pressure in the cyl7nders 35 being released for the
above described relative rotation between the driving and driven clutch
members to take place to align the balls 23 with the next adjacent torque
transmitting abutments. Where relative rotation between the clutch parts
takes place relatively slowly and/or the torque transmitting abutments are
disposed so that the balls become aligned only after a complete revolution
between the clutch parts, there may be insufficient time for the balls to
become aligned with the next adjacent receiving means before the clutch
pressure has fallen. In this case the springs 94û will have biased the clutch
plate 21, by virtue of engagement of the shoulder 961b therewith to the left
and hence have moved the driven clutch plate 20 to the left by virtue of
engagement of the balls 23 therewith. When such movement occurs, the balls
23 will have been moved out of engagement with the driving clutch plate 918
and hence further relqtive rotation with the cage plate 21 and clutch piate 20
will not take placeO In this case, the balls 23 will not be engaged with an
abutment 25 but will still be maintained spaced out of engagement with the
- 19- ~3~6~31
clutch plate 918 by virtue of the above described movement of the cage plate
21 and clutch plate 2û to the left.
In a modification, shown in Figure 9a, instead of providing the shoulder
961 b to engage the cage plate 21, the cage plate is engageable by an inturned
flange lOû2 provided on a cylindrical sleeve lOûO, fastened by screws 1001 to
the driven clutch piate 20. In this case the ring 961 and associated biasing
components such as the pin 9~2, springs 94û and annular member 96û, provide
a further biasing means rather than a cage biasing means and the cage is
controlled by the inturned-flange lOû2.
Referring now to Figure 10, thlere is shown a clutch which is essentially
similar to the clutch described with reference to Figure 9. In this
embodiment the driving member lû carries a gear 12 bolted thereto by se~
screws 13 and roll pins, not shown, in a sirnilar manner to that described
hereinbefore with reference to Figure 1. In this embodiment it is the gear 12
which is connected to an apparatus to be driven by the clutch and the
member 11 comprises a driving member.
The gear 12 houses bearings 19 which, in the present example, are taper
roller bearings. The taper roller bearings 19 have inner races 19a which
instead of being carried by the member 11 are carried in a recess 1060
provided on a massive and strong static member 1061. The static member
1061 has a stepped internal passage 1062 in the larger diameter part 1063 of
which is received fhe outer race 1064a of a double ballbearing 1064, the inner
race lû64b of which carries one end of an extension part lû65 of the member
I l. The member 11 has an internal passage 1066 in which is received the part
1065 which is connected, at the end 1067 thereof, to a motor which is to
drive the clutch. This embodiment is particularly applicable to a printing
press where the parts driven by the gear 12 may be desired to be maintained
stationary for a long period of time. Indeed the clutch may be operated in
such circumstances in a non-torque limiting manner in the sense that the air
pressure to the chambers 35 may be deliberateh~ relieved so as to disconnect
the drive irrespective of any torque limiting situation.
By providing the bearing configuration described hereinbefore, and in
particular by mounting the bearings 19 on the static member 106i, there is no
risk of drive being transmitted through the clutch by virtue of the bearings 19
wholly or partially seizing up. Therefore, if maintenance is being carried out
on a machine driven by the gear 12 then there is no risk of an operative being
injured due to the apparatus starting to operate as a result of the bearings 19
seizing up, since tile member 11 which continues to rotate is disposed within
the massive static member lû61 and should the bearings lû64 seize up, then
-20- 131~131
the loads would be accommodated by the massive static member 1061 and not
be transmitted to the bearings 19 and hence not transmitted to the gear 12
and hence to the machinery to be driven. Of course, the same safety factor
is provided if the drive part is reversed, that is to say, if the member
connected to the part 1067 is static and the drive is applied through the gear
12.
Referring now to Figure I i, there is shown a modification which is
applicable to all the previously described embodiments. In the previously
described embodiments the pressure of air in the cylinders 35 has been
relieved by virtue of engagement of a relieving means operating means 53
operated by an actuating disc 52. In Figure 11 the relieving means comprises,
alternatively, a valve 1111 which is operative, as hereinafter to be described,
to release the air pressure from within the cylinder 35 when the piston 34 has
been moved to the left, in Figure 11, as a result of disengagement of the balls
23 from their associated recesses 24, 25 as hereinbefore described.
The valve 1111 comprises a valve head 1112 in sealing engagement with
an O-ring 1113 retained within a bore 1114 by a sleeve 1115 which is itself
retained by an end cap 1116 through a further 0-ring 1117.
The head 1112 is connected by a frusto-conical part 1118 to a stem
1119 having a flange 1120 which is received in a recess 1121 in a member
1122 fixed, for example, by screws, to the piston 34. As the piston 34 is
moved to the left on disengagement of the clutch the frusto-conical part
1118 wili move into alignment with the O-ring 1113 thereby providing a
passage for air from the interior of the cylinder 35 to a passage 1123.
The passage 1123 is arranged to be of larger cross-sectional area than
the passage, not shown, by which air is introduced into the chamber 35.
Consequently, when the valve 1111 opens, air is exhausted more quickly than
it can be introduced into the cylinder 35 so that the pressure is relieved.
If desired, a microswitch 53 may be provided, actuated by a disc 52 so
as to interrupt the supply of air to the interior of the chamber 35.
Alternatively, an impulse air valve mqy be provided, which is actuated by the
flow of air through the passages 1123 to close a valve in the air supply to the
chambers 35. In all cases, because the passages 1123 are of greater cross-
sectional area than the corresponding inner passage to the associated
cylinders 35, the press~)re is relieved when the clutch disengages, thus there
is no risk of the clutch re-engaging or attempting to re-engage if for some
reason the microswitch 53 as described heretobefore fails to operate. For
-
-21- ~31~13~.
example, if the relative position o~ the microswitch 53 and disc 52 has been
damaged during maintenance operations. In the above described arrangement
where a microswitch corresponding to the microswitch 53 is provided to
switch off the air, then should this not operate, because oF damage or for any
other renson, the consequence is simply one of waste of air, so the pressure
would still be relieved because of the above mentioned difference in size
between the nir inlet and outlet passages.
Although the clutches described hereinbefore are primarily intended as
torque limiting clutches, if desired thley may be used as a simple clutch under
the control of an operator or of automatic operating means, drive being
transmitted when air under pressure 7s supplied to the cylinder 35 and drive
being disconnected when the air supply thereto is relieved by appropriate
mechanism in the air supply means.
The above described embodiments are not regarded as being exhaustive
and other modifications are possible to provide appropriate means for
controlling the cage plate so that the cage plate mqintains ~he balls out of
position for engagement with the torque transmitting abutments in one of the
clutch members.
In all the previously described embodiments re-engagement is achieved
simply by applying the air pressure to the pistons 34 so that the recesses 25 inthe driven clutch plate 2û are moved into torque transmittin~ engagement
with the balls 23 when they become suitably aligned therewith as a result of
the relative rotation between the driving and driven clutch members since in
these embodiments the balls 23 are already in engagement with the torque
transmitting abutments in the driving clutch plate 18.
In a further modification, not shown, which can be applied to all the
previously described embodiments; a receiving means separate from the
torque trcnsmitting elements may be provided, for example, by providing
similarly shaped frusto-conical recesses in the driving plate 18 to the torque
transmitting abutments therein but disposed angularly intermediate adjacent
torque transmitting abutments. In this embodiment to reset the clutch it
would be necessary to move the torque transmitting elements out of the
receiving means and move them into position for engagement with drive
transmitting abutments in the driving plate 18, for example, by rotating the
cage plate relative to the driving plate 18 by suitable means and then
reapplying the air pressure to the pistons 34 so that the torque transmitting
abutments in the driven plate 20 would move into torque transmitting
engagement with the balls 23 when they become angularly aligned therewith
-22- ~3~13~
as a result of the relctive rotation between the driving and driven clutch
members.
