Note: Descriptions are shown in the official language in which they were submitted.
~)66075
This inventio~ relates to mechanical transmissions,
the expression "mechan~cal transmissionsi' being intended to
include both load transmissions and motion transmis~ions.
For example, a device in accordance with the invention may
be intended primarily to prevent or restrict relative
motion between two bodies under load, as in a brake or to
transmit motion under load as in a clutch or coupling, in
which case, it is essential~y a load transmitter. On the
other hand, the device may be intended principally to
transmit motion in cases where the actual load is quite
small, as in the case of a control handle or lever, so that
it is primarily a motion transmitter.
In one particular application of the i~vention, it
provides a unidirectional bearing or free wheel device.
ConventionallD such a unidirectional motion transmitting
device usually comprises a drW ng and a driven member, with
an arrangement operative between the driving and driven
member~ to provide a wedging action in one direction Or
motion, but which releases the wedging action in the other
direction of motion~ When the wedging action is operative,
the driving and driven members are locked and cannot move
relatively to qach other, whereas when the wedging action
is inoperative, the driving and driven members can have
relative motion. ~hus in a free-wheel device for example,
there may be a shaft surrounded by a sleeve, with a
wedging arrangement between the shaft and the sleeve. In
one direction of rotation of the sleeve about the shaft,
the wedge is operative, and if the shaft i9 locked against
rotation, then the sleeve c~nnot turn about the shaft~ In
- 2
'~9
~ ,
. . . . . - , .
~0~;0~5
the opposite direction of the sleeve about the shaft however,
the wedging action is inoperative, and the sleeve can rotate.
One of the disadvantages of conventional unidirectional
motion transmitting devices is that the wedging apparatus
tends to be relatively complex and therefore expensive and
it is an object Or the present invention to provide a
unidirectional motion transmitting device, which is cheaper
to construct than conventional devices of this kind. It i8
to be understood however that the scope of the invention is not
restricted to unidirectional motion transmitters.
he invention may also be used to provide a load-limiting
device.
~or convenience, reference will be made throughout the
specification to driving and driven members, but it is to
be understood that in some applications of the invention r
there may be no appreciable movement, but only a transmission
load; in such a case the terms "driving" and "driven" are used
in the sense of the load applying and the load sustaining
member respectively. ~ikewise any reference to relative 't'
movement between the driving and driven members is to be
taken to include any tendency for movement under load.
According to this invention a mechanical transmission
comprises a driving member and a driven member with a
transmission element operative between said driving and
driven members, the transmission element itself comprising a
- multiplicity of filament struts arranged so that there is a
series of struts in both the longitudinal and lateral aspects
of the element, said struts being held together by a flexible
foundation, which engages with one of said driving and driven
;30 members, and projecting from the foundation towards the other
of said driving and driven members, the perpendicular distance
between said driving and driven members being less than the
~.
I, ~.
. " ~ . . . .
- ~0f~6075 ~ ~
perpendicular depth of said transmission element, when the
struts are not under load, whereby each strut is placed
in compression, but its angle of inclination to the flexible
foundation remains such that the frictional force acting
between the "free" end of the strut and the other of said
driving and driven members is sufficient to ensure that in
one direction of relative motion between the driving and
driven members, the angle between the struts and the foundation f
tends to increase, the arrangement ensuring that in the
opposite direction of relative motion, the angle between the
struts and the foundation does not tend to increase.
Now~ with such an arrangement in one direction (referred
to as "permitted direction") of relative movement the
frictional force between the ends of the struts and the driving
or driven member with which they engage tends to decrease the
angle of slope of the struts relatively to the foundation, but
in the opposite ("prohibited") direction of relative
movement, the frictional force between the ends of the
i struts and the driving or driven member with which they
engage tends to increase the angle of slope of the struts
relatively to the foundation. Since the transmission
element is adapted to engage with both the driving and
driven members, any tendency for the struts to approach
the perpendicuar (i.e. increase in the angle of slope)
causes them to act as wedges between the driving and
driven members and this inh;bits relative motion between
the driving and driven members. Providing there are
` sufficient struts the cumulative resistance to motion
produced by this wedge action will be sufficient to
prevent relative movement in the prohibitied direction. A
r
,
,
.. . . , ~ , .:
10~607S
limiting co~dition occur8 however when the str~ts buckle
under the applied load.
Any tendency for the struts to recede from the
perpendicular (i.e. decrease in the angle of slope)
reduces the friction between the struts and the driving
or driven member with which they engage so that there is
comparatively little frictional resistance to the permitted `;
relative movement. On the other hand, the angle between
the struts and the perpendicular must not be too great, or
they would not provide the wedging action when required.
If the device is required to act only as a clutch or
coupling, it will always operate in the "prohibited"
direction to effectively couple the driving and driven
members together. If it is required to act as a free-wheel
device, it will couple the driving and driven members
together in the "prohibited" direction, but uncouple them
in the "permitted" direction. If the device is required to
act as a load permitting device, then it must be so designed
that the struts will buckle so as not to transmit load in
the prohibited direction at a critical load.
It is preferred that the angle of the struts relatively
to their foundation is in the range 75 to 85. In
the preferred construction the angle is about 80.
~he transmission element may comprise pins set into
- but projecting from the flexible foundationO In that case,
the flexibility of the foundation may be such that it
permits angular yielding of the pins with respect to the
surface of the foundation from which the pins project,
when said pins are under load. It is an important
',~
~'~'`' .
: - .
.
.
6075
characteristic of the flexible foundation that it
is resilient so that when load is released the wires
"recover", that is to say, the wires return to their
original angle of slope. ~ence when the wires are under
load, the foundation is always urging the wires towards
their unloaded position. ~he pins may have a degree
of resilience to permit said pins to bend under load.
In a preferred construction, the pins are formed on
two-legged staples driven through the foundation from the
underside, so that in structure, the transmission element
resembles card clothing. It will be understood however
that the"card clothing" may have in some instances pins
which would be unsuitable for actual carding operations.
For example, very short thick pins are sometimes desirable
be¢ause of their good load transmitting peroperties. ~he
"card clothing" can be produced by known techniques, and
is therefore relatively cheap and certainly a transmission
element formed of card clothing will be cheaper to produce
and to fit then the conventional ball-and-wedge type
unidirectional motion transmitting devices.
The invention is applicable to both linear and
rotary motion transmitting devices. In either case the
transmitting element is arranged with the struts sloping
away from the foundation in the direction of the
"permitted" movement. ~he foundation may be secured to
the driving a~d driven member, on which it is provided
but in some cases it will be unnecessary, because the
- 6 -
. . . .
1066~75
._ .
wedgin~ action will provide the nccessary lock between
the foundation and the driving or driven member.
If the device is a rotary onc for example; then it
will be necessary to arr(q~nge the transmitting element in
a cylindrical form, which may be with th~ struts on the
outside of the foundation in the same wa~ that card
clothin~ i9 usually wrapped on to ~ carding m~chine
roller, or with the struts on the inside of the
foundation (i,e. the reverse of the conventional card
clothing arrangement)~ In either case, if the device is
required to transmit load or motion in only one direction~
then the struts will point in one cylindric~1 direction -
clockwise or anticlockwise. If on the other hand, the
rot~r~ device is required to transmit load or motion in
both directions~ it will hnve struts sloping in both
directions. Ihis is most casily achieved by having two
sets of struts preferably arranged in side-by-side bands.
If the device is a linear one, then the card clothing
will be arranged with the wires pointing towards one end
or thc other of the device rather than in a cylindrical
direction. Again, if the devicc is required to transmit
load or motion in both directions, it will have two sets
of struts sloping in opposite directions.
A device constructed in accordance with the invention
can be used as a load transmitting device. ~he drive from
tho driving to the driven member will, of course, be in
the direction which isr~sistC~' by the struts, so that they
effectively prevent relative movement between the driving
and driven members. In this condition an axial
-- 7
,
:
1~66075
co~pressive load i5 applied to each wire. Now it has been
shown that there is a critical load at which a column
(in this case one of the struts) will buckle. Hence~
there will be a critical load at which buckling will occur,
and the drive will be disconnected when this happens. Ihis
load will be predictable at least on an empirical basis,
within a reasonable margin of error and therefore it is
possible to design a device having a li~ited lond
transmitting c~pacity.
Some embodiments of the invention include both driving
and driven members, with the transmis3ion element located
between them. In other embodiments however~ there is only
a driving or a driven member with the tran~mission elemerlt
mounted on it ready to receive an item which will provide a
driven or a driving member. For examplo, in ona embodimont~
the driving ~e~ber is a workholder of a machine tool, and
the workpiece itself bccomes the driven member when it is
received by the workholder.
Several devices each in accordance with the invention,
will now be described by wa~ of examplcs only, with
reference to the accompanying drawings, in which:-
Fi~ure 1 is a diagrammatic representation of a
- transmissio~ element in an unrestrained condition,
Figure 2 is a diagram showing the principle on which
the invention operates,
Figure 3 is an axial cross-section through a
free-wheel device,
Figure 4 is a section on the line IV-IV in Figure 3,
Fi~ure 5 is a cross-section through a unidirectional
~0 linear bearing,
- 8
, ~ .
.. ,. , . ... , , . . . . . .
~. , . . . . ~ - . ~.
:.: . . . . .
10~6075
, . .
Figure 6 is a sectioIl through ~ workholding device
for use in a machine tool showing ~ workpiece in position,
Figure 7 is a section through an alternative
workh~ng device, with a workpiece in position,
Figure 8 is a section through a flexible coupling,
Figure 9 is a dingram~atic repre~entntion of the
driving arrangcment for .~n item of machincry~
Fi~urc 10 is a detail scction through a coupling
shown in Figure 9,
Figur~ 11 is a section through a clutch,
Figure 12 is a section through ~ grinding attachment,
~nd
Figure 13 is a perspective view of a bottle opener.
~he principle on which the invention is based is
illustrated in Figures 1 and 2. In these dr~wingQ 10
reprcsents tho flexible found~tion of ~ piecc of card
clothing as used in the textile industry, and 12 a single
wir~ of that card clothing. In practice a large numbex of
two lcgged wire staples are pressed through thc
foundation 10, so that the crown of each staple engnges
with the undorside of the foundation and the legs extend
through and projcct above the top surface of the
foundation. As shown in Figure 1, wires are sct so that
they slope relatively to the surface of the foundation
at an angle ~ when in the "free" or unstressed condition~
Now it is the basis of the present invention that the
card clothing is used to tr.~nsmit load or motion between
two members, and in ~igure 2, there are shown a member
14 (which for present purposes will be regarded as
stationary) and a member 16 moveable in the direction
g
... . .
.; : ,' ` . .
.,
106~i075
of arrows A and B (i e. lincar ~otion parallel with the
surface of the foundation 10 and against or with the
slope of the wire 12).
~hc pcrpendicular h~ight of the card clothing in
the unrcstrained condition is H, but the facing surfaces
of the ~embers 14 and 16 is less than H b~ a distance x.
Hence, when the card clothing is placed betwee~ tha
members 14 and 16 thc wires 12 are deflected as shown
in Figure 2 so that the ~ngle R between thc tip portion
of the wire and thc foundation becomes ~ore acute, and
this increases the friction between the "free" ends of
the wires 12 and the surfaces of the member 16 and thus
introduces a pre-load into the system~
If a load is then applied to the ~cmber 16 in the
direction of the nrrow ~, ~ovement of the ~enber 16 is
resisted by the frictional engagcmcnt of the wires 12, and
in fact thc wiros tend to move towards the str~i~ht
condition thus increasing the frictional force bctwcen the
members 14 ~nd 16. In this way the card clothing acts to
lock the members 14 and 16 togcther to prevent relative
movement between them.
If on the other hand~ the member 16 attcmpts to
move in the direction of the arrow B, although there is
some frictional force opposing this movement, it becomes
considerably less than in the direction A, because the
wires 12 tend to be pressed downwardly (i.e. the angle R
is reduced) and hence the frictional load is reduced.
It will b~ apparent th~t b~ suitable design, it is
possible to achieve a variety of results. ~hus, for
3 exa~ple, the pre-load distance x can be made ver~ sm~ll
., .
- 10
,
.
.: . . .. .
.
~, ' ':- ' . ' '
~; . . . - .
1~)ti6~75
-so that the tips of the wires only just engage with the
surface of the member 16, because the tendency of the
wires to straighten when thc me~ber ~6 attenpts to nove
in tho dir~ction ~ will incroase thc frictional grip of
the card clothing betwecn the mer~bers 14 ~nd 16. On the
other hand with this very low prc;-loading, the ~embcr 16
is frec to move in tho dircction of the arrow B with vory
little frictional resistance. Conversely~ by increasing
the pre-load~ the forcc rcsisting relative movemcnt
between the two ~e~bers 14 and 16 can bc increased, but
thero is a linit to this, since if the c~ngle R becomes
too small, the locking force is reduced.
It will be apparent, that if the load in the wires in
the direction A beco~es too great, then the wires buckle
and allow relative ~ovement betwe~n the me~bors 14 and 16.
~his is a limiting condition, and it is possiblc to design
the apparatus (though only by e~pirical metho~) so that
it fails by buckling of the wires at a critical load.
It ~ust be pointed out however, that once the wires hc~ve
buckled, the load transnitting charactcristics are changed
and hence in many cases, the apparatu~ would not bc
reuseablc.
Certain features should be noted before leaving this
description of the basic principles:-
(1) Varintions in the angle of slopc Q of the wires
I can be achieved wither by flexing of the foundation 10
I (the wire re~aining straight, but moving in the
foundation) or by bending of the wire (due to its
resilience) or by a combination of both these effects~
.
..__. ... . . . .
! ~
1066~75
(2) As has been indicated, there are limits on the
angle of slop~ for effective action and for all practical
purposes the angle Q should lie within the range 75 to
85. An angle of slope of about 80 has been found
particularly effective.
(3) Although references have becn made to card
clothing, tests havc shown that for ~any purposes~ the
wires should be of short protrusion and relativel~ l~rge
di~neter. ~hus, for exa~ple, in one practical e~bodi~ent,
the wires h~ve a dianeter of 0.025 inches and are only
0.125 inches long. ~his n~y be quite unsuitable for use
as card clothing, and it can only be said that the ~aterial
used in the invention resembles card clothing in that it
conprises wire pins set in and projecting fro~ a flexible
foundation and can be ~anufactured by the sa~e techni~ue
as that used to m~nufacture card clothing. ~he clothing
used in the various embodiments hereinafter described will
therefore be referred to as "clutch-clothing". In so~e
of the-dr~wings, the length of the wire has been exaggerated
for clarity.
(4) It will generally be desirable to use straight
wires as have been illustrated, but it ~ay be possible to
use kneed wire in some applications (c.g. where a low
buckling load is desirable).
The first practic~l ~nbodi~ent is a free-wheel device
illustrated in ~igures 3 an~ 4~ ~here is a gear wheel 20
;an~ a shaft 22 passing through the gear wheel, and the
object of the device is to transnit rotary notion fro~
~the shaft 22 to the wheel 20 in the direction C, but not
ito transnit ~otion in the reverse direction~
. . . .. .... . . .... . . .
- 12 - ~
.. - . . . .
.
1066C)75
! A driving ~enber 24 is keyed on to the shaft 22,
this driving nember being generally cylindrical, ~nd
having locations for the inner races of b~ll bearings
26 and 28. Ihe gcar wheel 20 has a boss 30 by nc~ns of
which it is fr~c to rotate on the bcarings 26 and 28
~nd this arrange~cnt cnsures n correct concentricity
between the shaft 22 and the gear wheel 20.
It will be observed that there is an (Innular space 32
between the boss 30 and the outside of the driving ~enber
24~ and a trans~ission ele~ent 34 is fitted to the me~ber
24 so that it occupies thc space 32~ I`he trans~ission
eler-ent co~prises clutch-clothing having pins 36 projecting
fro~ a flexible foundation 38. ~ince the space 32 is of
short length, a single strip of clutch-clothing is used~
but if the device were of considerable length it ~ignt be
necessary to provide ~ series of strips applied to the
driving member 24 in a side-by-side arrangement.
~ he foundation 38 is stuck to the outside of the
nember 24 for ease of assembly, but this is not essentinl
to the operation of the device.
It will be observed by reference to ~igure 4, that
the clutch-clothing wires 36 are inclined so that they
point in,a circumferential direction~ in this particular
inst~nce, the wires pointing away fro~ the foundation
in ~ generally anti-clockwise direction. ~he radial
depth of the space 32 is slightly less than the ,
unrestrained height H of the clutch-clothing, so that
the latter is prc-loaded as previously described. ~he
wires will be bent as the ~riving ~eMber 24 is introduced
_,~xially into the bore of the boss 30
- 13 _
.. ,., ., ,.: ~, .
~, . .......... ''
1~66~75
Supposing th~t the shaftt 22 i9 rotated in ~ ~
elockwise direction, then the outer extre~ities of the
wires ~6 will drag ag?inst the insidc surface of the boss
30, but this will tend to force thc wircs even furthor
towards thc sh~ft, thus tcnding to reduce the friction
b~tween the wires ~nd the boss 30. Henee, it is possible
to arrange the device so that in this direction of
nove~ent of the shaft 22, no ~otion is tr~nsnitted to
the ge~r whecl 20.
However, if the shaft 10 is rotated in an ~nti-
eloekwise direction, (arrow C) then e~eh wire 36 willtend
to nove towards a nore upright position, thus inereasing ~ ;~
the aeute angle between the wire and the foundation. Ihis
provides a wedging aetion between the driving shaft 22 and
the boss 30, ~nd henee the two b~co~e loeked together
and ~otion is trans~itted fron the driving shaft 22 to the
wheel 20. Ihe boss 30 becones the driven me~ber of a
eluteh in ~hich the eluteh-elothing 34 aets as a
tra~itting ele~ent.
It will be appreciated, that there nust bc an adequate
nunber of wircs, to transnit the nccess~r~ torsional load
between the driving shaft 22 and the boss 30. Eowever
the elutch-cl~thing eo~pris~s a ~ultiplieity of wires
over a relatively snall are~, .~nd it h.~s been found that
the torsional tr~n~nitting power of cluteh-elothing
arr~nged in the ~nner illustrated in Figure 4 is quite
high,
Referring now to the linear bearing arrangenent
whieh is shown in Figure 5, (this being another b~sie
forn of the invention) there is a stationary shaft 40t
_ 14 -
.. ..
`: :
10~6~)75
~nd a sleeve 42 co~xial with the sha~t 40, and slidable
longitudinally thereof, in the direction of the ~rrow D
in the drawing. The borc of the sleevo 42 is
considcrably largcr than the outside dia~etcr of the
shaft 40, so that there is a radial gap betwecn the two,
and within this gap there is fitted a clutch-clothing
notio~ transnitting device 44 having a foundation 4~j
and wires 48. At ~ach end of the notion transnitting
device 44, there is provided ~n oil seal 50.
In this construction~ the foundation 46 is for~ed
into a cylinder, with thc wires 48 on thc inside, which
is the reverse of th~ usual carding ~achine arrangenent.
~he foundation is in eng~genent with the bore of the
- sleeve 42, and the ti~ of the wires 48 are in
engagement with the periphcry of the shaft 40. It is to
be noted however th~t in this construction, the wires 48
are not inclined in a cylindrical direction, but are
inclined from the foundation 465 towaIds the lefthand
end of the sleeve as seen i~ the drawi~g.
It is also preferred in this type of arrangenent,
to use clutch-clothing, in which the foundation is nade
of synthetic rubber such as neoprene~ ~nd to fill the
bearing in the space bctwecn the two oil se2ls, with a
lubricating oil.
If the sl~ve 42 ~ttenpts to nove in the direction
of the ~rr~w D~ then the wires 48 will tend to deflect
towards the foundation 46, nnd this will reducc the
frictional enga~c~ncnt betwcen thc wircs 48 and the
shaft 40, thus pcrnitt-ng the sleeve 42 to nove along
the sh~ft. However, i~ it is attenptQd to nove the sleeve
- 15 -
" , , - ~ ~6
~0~6075
42 in the op~osite direction, then the wires 48 will tend
to nove towards the perpendicular, and will have a
wedging action resisting linear ~otion of the sleeve 42.
It will be ~preciatcd that the linear be~ring
illustrated in Figure 5 h~s nany possible applications
industrially, but it will be nentioned here that it has
beon found conv~nient for use in thc nounting o~uip~ent
used ~or ~ounting so-called ~et~llic t~pe card clothing
wire on c~rding ~achine rollers~ ~his nounting equip~cnt ~ -
includes n rigid and stationary tube extcnding across
the width of th~ roller which is to bc covered with card
clothing, this tube providing in effect the shaft 40
illustrated in ~igure 5. ~he ~ctual ~echanis~ for guiding
the netallic wire on to the cylinder or roller, has to
tr~verse longitudinally of the nounting tube, but it is
essential that it should not be able to yield in a
direction opposite to its direction of traverse. A
relatively conplicated ~echanis~ is conventionally used
to ensure that the wires guiding ~echanisn does not nove
in the wrong direction on the rigid tube9 but it has
been found that this nech~nisn can be conpletely replaced
by a sinple clutch-clothing type bearing as illustrated
- in Figure 5.
It is also thought that the invention will find
~5 practical .~pplication in the case of relatively slow
noving control devices, which are required to have
unidirectional notion tr~nsnitting effect.
As illustrated in Figures 6 ~nd 7, the invention
can be used to provide a workholder for use in a ~achine
-30 tool. In the arrangenent shown in Figure 6, a workholder
- 16 -
1066075 - .
60 is adapted~ by ~e~ns not shown, to be secured to the ;~
spindle of . ~achine tool so that it c~n be rotated about
its own longitudin~l axis. Flexible clutch-clothing
is received in the bore 64 of the workholder, with the
teeth pointin~ inw~rdly ~nd in a cylindric~ direction.
h workpiece 66 (which is illustrated ~s a hollow
cylindrical object) is pushed into the "bore" provided
by the tips of the clutch-clothing wires, a~d is he~d
there by frictional eng?~ge~ent with the wires. ~he
workhclder 60 is then the drivi~g ~e~ber and the workpiece
66 is the driven ~e~ber. ~he clutch-clothing 62 will
transmit rotary ~otion fro~ the workholder to the
workpiece in one direction cnly, ~nd this is the direction
required for processing the workpiece on the machine.
15- - A workholder constructed ~s shown in Fi~ure 6 c~n be
used for ex~nple to grip thin walled or delicate
co~ponents which might be distorted by the Ja~s of a
conventional chuck or collett~ It could ~lso be used to
grip non-ferrous workpieces which cannot bc held by
~agnetic tables. Since the wires of the cl~tch-clothing
62 ~re vertic~l (as seen in longitudinal section through
the workholder) there is little resistance to the wor~piece
being pushed axiall~ into the workholder. It will be
appreciated, th~t the workpiece can be ~uickly ~nd easily i
mounted and releasea, without thc necessit~ ~or operating
devices ~uch as chuck keys, ~nd hence the workholder
is of especial adv.~ntage in repetitive high production
rate situations.
It is envisaged th~t the workholder shown in ~igure 6
will be ~ainly used in ~achine processes wherein the
- 17 -
.
.
1066~75
forces acting on the workpiece are substantially entirely
radial, and quite s~all. For ex~ple, the workholder ~ay
be uscd in nachines for grinding, polishing, netal
spraying, netal coating and welding.
In Figur~ 7, thore is illustrated an internal driving
ne~ber 70, which is requircd to hold and rotate a relatively
l~rge dianeter hollow cylindrical workpiece 72~ In this
arrangc~ent, clutch-clothing 74 is applicd to the outer
cylindrical surface of thc driving nember~ with the wires
~ pointing outwardlyO ~hc borc of the workpiecc is a close
fit on the tips of the wires and hcncc thc wires grip the
workpioce internallyO It is cxpected that this arrange~nt
will be used in nachines sinilar to those in which the
workholder 60 will bc used, and it possesses the sa~e
advant~ges as that workholder~
~eferring now to Figure 8, there are shoh~n a driving
shaft 80 and a driven shaft 82, which are intended to be
co~xial, and ~ coupling 84 joining the two shafts and intended
to transnit torque fron the shaft 80 to the shaft 82. ~he
coupling 84 has a cylindrical ~uff 86 within which is
secured clutch-clothing 88, with the wires directed
inwardly~ ~he "bore'l of the wires 88 is a slight
- interference fit on each of the shafts 80 and 82~ so
that the coupling grips the shafts and is .able to
transnit torque - i~ one direction of rotQtion only.
H~nce, the coupling is a unidirectional coupling.
In ~igure 8, the shaf~s 80 nnd 82 are shown
nisaligned, ~d it will be appreciated that the
nisalign~ent has been grcatly exaggerated, to illustrate
the oper~tion of the coupling. ~hc wires of the
_ 18 -
1066075
clutch-clothing 88 will yield to a lir~ited cx*cnt Oll
one side or th~ oth~r of th~ lon~itudinal IXiS of c~ch
sh.~ft to acco~odate the ~isali~nnentO Ihus the
coupling is effcctiv~ as a flcxibie coupling~
In practice, it will probably be necessary to fit
collars on the shafts 80 and 82 to prevcnt axial
nove~ent of the coupling.
If the coupling is required to trans~it ~otion
in both directions, then it will be n~c~ssar~ to provide
strips of clutch-clothing Ol1 the inside of the ~uff 86,
so that therc are two sets of wires in engagenent with
each shaft 80 and 82, the two sets of wires being sloped
in opposite directions~ ~hus in one direction of rotation
one set of clutch-clothing wires transnit notion and the
other set si~ply slide around thc shnft~ but in the
opposite~ dircction of rotation the rolcs of the two sets
of clutch-clothing wires is rev~rsed.
Figures 9 an~ 10 illustrate a type of driving
arr~nge~ent which is frequentl~ encountered in industry.
hn electric ~otor 90, which is the princ nover drives a
speed reduction gearbox 92 through a coupling 94. ~he
gearbox 92 ~ay be a worn-c~nd-whcel type gearbox for ex~nple,
in which the efficiency of the gearing when the drive is
reversed, is so low that the gearbox provides an
irreversible driving unit.
Ihe output shaft 96 of the ~earbox 92 is connected
via a free-wheel coupling 98 to ~e apparatus 100, which
has to be driv~n. I~his apparatus nay be any one of a
variety of ~achines, but it is a characteristic of the
~0 apparatus that it has a large nass or a large inertia~
- 19 _
.
1066~75 ~
~he frec-wheel coupling 98 i8 shown in Figurc 10 .~nd
ço~prises a drivin~ shaft 102 and c. driven-shaft 104~ ~hc
latter h~s an ~nlarged cnd 106 with a bore 108 and clutch-
clothing 110 fitted on thc shaft 102 with its wires
directed outw~rdly has thc tips of its wires eng~ging with
the bore 108, to provide n unidirectional driving
arr~ngenent as described in the previous ex~nples.
If the elGctricity suppl~ to the ~otor 90 fails for
any reason, then the driven .~ppar~tus 100 will decellerata
at a slower rate than the uotor 90 (owing to its greater
inertin) and thus weuld overrun the notor 90 ~d attcnpt
to drive the motor throu~ the ge~rbox 92. ~his would
involve a reverse drive through the gearbox which could
~.
seriously d~magc the transrlission, if the latter includes
~n irreversible gearing such as a wor~-~nd-wornwheel.
However, if tha appara~ 100 ov~rruns the output shaft 96,
the free-wheel effect of the coupling 98 allows thc
apparatus 100 to decallcrate at its own rate without
~ttenpting to driva tha ~otor through the g~rbox 92. ~he
coupling 98 thereforc protects the tr~ns~ission ag~inst
excessive loads in the case of a sudden failure of the
electricity supply.
An arr.~ngencnt sinilar to that shown in ~igures 9 ~nd
10 can be used as a torque li~iting device. Since each wire
of the clutch-clothing will buckle at a critical ~xial load,
the coupling 98 will h~ve a critical load at which the wires
will all buckle (or a sufficient nurlber will buckle) to
render the coupling inaffective for tr~ns~ittin~ torque.
Thercforc, it is possible to design the coupling 78 to
tr3Lsnit only ~ linited torque to protect the ~pp~r~tus
_ 20 -
~ r~_-
~()66~75
which is boing drivan.
. ~his pro~idcs ~ s.~fety fc~turo which~c.~n only be used
once, since once the buckling has occurrcd, the coupling
98 will prob~bly bo useless.
It will be appreciated th~t ~ sinsle coupling nay
enbody the flexible fe~turc dcscribed with refere~ce
to Figure 8 ~nd the free-whecl and torque liniti~g
functions described with reference to ~iguree ~ and 10,
~ning ~ow to Figure 1'1, there is illustrated
clutch for coupling a driving shaft 120 to ~ co~uQal
dri~en shaf t 122~ ~he drivin~ shaft 120 is for~ed with a
boss 124 and this is received in the bore of ~n enl~rged
boss 126 forned in a coupling ~e~ber 128~ with a ~adial
sp~ce betwecn the boss 124 and the bore of the boss 126.
~he coupling ~e~ber 128 is slid~ble ~xially on a splined
portion 130 of tha driv~n shaft 122, ~na there is ~n _~
a~nul~r groove 1~2 in the nenber 128 to reccive ~ fork
(not shown) for ~oving the coupling nc~ber .~xi~lly.
~wo sets of clutch-clothing 134 and 1~6 are provided
on the inside of the boss 126, onc with its wires sloping
in one circu~ferenti~l direction (as in the arr~ngenent
shown in Figuro 4) ~nd the othcr with its wires sloping in
the opposite direction. ~he clutch-clothing is arr~nged
to operate between tho coupling ~enbor 128 and tho boss
124 in the driving shaft 120 and the wires are put under
sone pre-load, as previously described-when either set of
wires is brought on to the boss-124 by axial displace~ant
-of the ccupli~g De~ber 128. ~o facilitate ~he
engage~ent of th~ wires cn the boss 124 by ~xinl ~ovc~ent,
3 the boss is for~ed with ch~fcrs 140 ~nd 142 at its ends.
- 21 -
~066~7s
When the coupling ~e~ber 128 is in the position
s-hown in Fi~ure 11, nction will be tr~nsnitted to the
sh~ft 122 through the elutch-elothing 134 in a first
direetion of rot~tion7 but if the driving sh~ft 120 is
rct~tad in the opposite direction, it will free-wheel
inside the coupling ~enber 128 I~ the eluteh is required
tG work in the oppositc dircction~ thcn the nenber 128
is slid along the shaft 122 to bring the eluteh-elothing
136 cn to the boss 124. Of eourse, if the cluteh is ~nl~
required to operate in one direetion~ then the eoupling
nenber 128 c~n be sllorter and the eluteh-elothing 1~4 ean
be dispensed with.
~igure 12 illustr~tes anoth~r ~pplication of the
invention~ in this e~se to a ~ri~ding attach~ent. A
drivin~ spindle 150 h~s an e~larged boss 152 on whieh is
fitted eluteh-clothing 154 with the wires pointing
outw~rdly and sloping eireu~ferentially. A thin ~br~sive
sleeve 156 is thre~ded cn to the eluteh-elothing 154,
so th2t it est~blishes ~ driving eonncetion with the
spindle 150~ Ihe sleeve 156 ean then be rotated (at least
in onc direetion) by the spindle 1500
~his applic~ticn is one wherein it n~y be desir~ble
to h~ve a plurality of strips of eluteh-elothing
sida-by-side, with the wires of alternate strips sloping
in opposite direetions. It also is ~n instL~nee where
tha wires n~y be quite long and very flexible (even
perhe~ps, kneed) so th~t the sleeve 156 is per~itted sone
inward defleetion in use, whercby the 2quipnent can be
used to ~rind irregullrly shaped objccts.
_ 22
~066~75
~igurc 13 shows ~ tot~lly diffcr~nt application
of the invcntion, for renovin~ the screw-on c~ps o~
bottles. ~ br~cket 160 is ad~ptcd to be sccured to Q
w~ll, shel~ or bar counter, ~nd has a p~ir of outwL~rdl~
spl~yed linbs 162 ~nd 164. Clutch-clothing 166 nnd 168
is bGnded to the inside f~ces of the linbs 162 and 164
respectively, ~nd whereas the wires of the cIothing 166
slope upw~rdly, those of the clothing 168 slope
do~nwardly.
In use, the c~p 170 of a bottle 172 ls pressed dcwn
into the wires of the two sets of clothing as far as
possible~ (It will ~e appreciated, that b~ virtuc of the
V-shape of the li~bs 162 ~d 164, it is possible to
~ccon~odate a rangc of sizes of cap 170). ~he bottle
is then rotated in a directiGn to unscrew the c~p ~nd
the clutch-clothing resists rotQtion of tha CQp thus
screwing it in the release direction. Ihis ex.~ple
indicates the widc r~nge of possible uses of the
invention.
It is possible to use the fe~tures of one
c~bodi~ent described ~bove with other e~bodi~ents.
.
- 23 -
.
