Improvements in Friction Clutches.
Year: 1899

page_text: Date of Application, 20th July, 1899-Accepted, 26th Aug., 1899
Improvements in Friction Clutches.
A communication by THE WERKSTÄTTE FÜR MASCHINENBAU, vormals DUCOMMUN,
Franklin Strasse, Mülhausen, Alsace, in the Empire of Germany, Machine
Makers.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester,
both in the County of Lancaster, 118, New Street, Birmingham, in the County
of Warwick, and 322, High Holborn, in the County of Middlesex, Civil Engineer,
do hereby declare the nature of. this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement: --
The friction clutches hitherto known by means of which a gentle connection
of the parts to be coupled is attained, must always be compulsorily thrown into
action. By this means however, there takes place a somewhat too sudden con-
nection of the parts, so that in case the driven part of the shaft is required to.
rotate heavy masses, the driving part of the shaft is excessively loaded on
initiating the movement and exposed to strain, so that frequently a breakage
of the shaft, or other interruption of working is unavoidable.
The friction clutches hitherto employed also have the drawback that when
they are connected and the driven part of the shaft has to overcome a greater
resistance, whether owing to the machine or the like connected with it being
suddenly overloaded, or owing to a foreign body falling therein, or finally by a
mishap to the transmission gear causing resistance, they, (that is the clutches),
do not disconnect automatically, but rather transmit forward the strain imparted
to them.
This invention has for its object a friction clutch in which the friction blocks
are radially movable, and bear by means of the centrifugal force produced in
them against the friction surface of the driven part, and carry the same with
them, always with a gradually increasing speed, up to the normal speed which
the driven part is to have, in case the latter .consists of heavy masses, such for
instance as a centrifugal machine.
If however the transmission through any circumstance suddenly meets with
resistance for instance by a foreign body falling into the gear or into the
machine, the friction clutch remains inactive, that is to say, is automatically
disconnected until the resistance is removed, and then it again automatically
comes into action.
A form of construction of this improved clutch is shown in the accompanying
drawings, Figs. 1 and 2 being vertical and horizontal sections of the same.
whilst Fig. 3 shows another arrangement with the clutch in vertical section and
the driving pulley in elevation Fig. 4 is a vertical section of a form of construc-

page_text: tion of the clutch in which the friction blocks only come into action when a
given number of revolutions is exceeded, and the excess power is transmitted
to another machine or a brake.
As shown in Figs. 1 and 2 the driving section a of the shaft is provided with
a hub having one or more arms b. On each of these arms a friction block c is
movably mounted and held in equipoise by means of a spring d; said friction
blocks bear against the inner surface of a hollow disc g fixed on the driven
shaft f.
The hollow disc is closed or covered laterally by a plate h mounted loosely on
the shaft a, and the casing g h, thus formed, is filled with a lubricating liquid,
through which an even friction between the blocks c and the disc g is secured.
When therefore the shaft a is set in rotation, the friction blocks move out-
wards owing to the centrifugal force produced therein, and thus grip and carry
with them in their rotation the casing, and thereby the driven shaft f. If the
latter be connected with heavy masses, these are set slowly in rotation at a
gradually increasing speed. If however a greater resistance be opposed to the
driven part, the friction blocks slip on the inner surface of the disc and only
again carry the latter with them after the resistance has ceased.
In the form of construction shown in Fig. 3 the casing g h is loosely mounted
on the driving shaft a and is also formed as a belt pulley.
Finally the clutch may be arranged so that it only comes into action when a
given speed of rotation is exceeded. By this means the advantage is obtained.
of being in a position to utilise in many cases power which would otherwise be
lost, or of preventing accidents arising from too great a number of revolutions.
If therefore a transmission gear, (by means of which for instance a machine is
driven, which must operate on something) be provided with such a clutch and
the latter be connected with a machine coming into action only in case of need,
or with a brake, the friction blocks will move outwards in case the resistance
to be overcome by the transmission suddenly decreases and the power is trans-
ferred to the other machine or to the brake, so that the power is again utilised
or consumed by the brake, and thereby any mishap is prevented.
This clutch can however be also very advantageously employed for such
electric lighting apparatuses as are driven by means of water power (where the
said clutch only comes into action after a maximum speed is exceeded) as, if the
water supply is inconstant, or variable, then measures must be adopted by means
of which the differences of pressure produced by the alteration of speed may be
avoided. For this object it is usual to avoid or at least diminish as far as
possible the eventual increase of pressure by providing the turbines with a
governor or by inserting an automatic resistance in the electric circuit. These
arrangements mean however always a loss of power which may be avoided if the
clutch herein before described be introduced in the transmission gear driving
the dynamo machine, and connecting the same with a dynamo machine which
feeds an accumulator battery. If the water level rises and thereby the number
of revolutions of the transmission gear is increased the dynamo machine con-
nected with the clutch will be set in operation and the surplus power utilised
whilst at the same time, increase of pressure and the damage resultant there-
from is avoided.
Fig. 4 shows a form of construction of the clutch in which the friction blocks
only come into action after a given number of revolutions are exceeded and the
power released is transmitted to another machine or to a brake. For this
object, each friction block is pressed against the shaft by means of a resistance
spring arranged in the said block, which spring acts against the centrifugal
force arising in each friction block. If however the regulation speed be
exceeded the centrifugal force.overcomes the resistance of the spring and the
clutch comes slowly into action.
This clutch works in both cases also as a regulator for the various working
apparatuses.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is:
1. A centrifugal friction clutch in which the friction blocks are moved radially
outwards by means of the centrifugal force arising therein, characterised by
the friction blocks being guided, in a casing filled with a lubricating liquid, on
radial arms extending to the friction surface with the object of maintaining
constant the friction co-efficients and avoiding any jamming of the brake-jaws
in their guides and securing the free mobility of the same in a radial direction
substantially as described.
2. A special form of construction of the centrifugal friction clutch herein-
before described characterised by the friction blocks in the closed casing, which
is filled with lubricating liquid and which are movable on radial arms, being
prevented from describing an outward radial movement by springs (i) with the
object of allowing the brakejaws to come into action only when a given number
of revolutions is exceeded, substantially as described.
Dated this 19th day of July 1899
WM. P. THOMPSON & Co.,
Agents.