Improvements in Devices for Transmitting Power, and Especially for Transmitting Power from Electric Motors used for the Propulsion of Vehicles.
Year: 1890

page_text: Date of Application, 2nd June, 1890
Complete Specification Left, 28th Feb., 1891-Accepted, 18th Apr., 1891
PROVISIONAL SPECIFICATION.
Improvements in Devices for Transmitting Power, and Especially for
Transmitting Power from Electric Motors used for the Propulsion
of Vehicles.
1, BENJAMIN JOSEPH BARNARD MILLS, of 23. Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of this inven-
tion, a communication to me from abroad by Edward Hibberd Johnson, of the
City, County, and State of New York, in the United States of America, Electrician,
to be as follows:-
The invention relates to devices for transmitting power or motion from a rotating
part or body to a part or body designed to be rotated thereby, or usually, from a
driving shaft to a driven shaft. Said invention was designed with especial reference
to the transmission of power from the armature of an electric motor to the axle of
a railway car to be propelled by the motor.
It is however in its more essential features adapted for use in apparatus or
machinery of any character in which power is to be transmitted from one shaft to
another.
The main objects of the present invention are to produce a simple and effective
device or apparatus in which the power-transmitting value or capacity of the
connection between the two parts will be constantly proportioned to the power
required, and which will enable the power to be applied gradually in starting.
Another object which is especially useful in electric railway cars is to enable the
driving shaft to be readily thrown out of gear with the axle when the car is on a
down grade, or when for other reasons this is desirable.
Heretofore attempts have been made to apply power gradually and in proportion
to the load, by the use of intermediate springs and also by frictional engagement.
Each of these plans has advantages and disadvantages which are well known.
The present invention is designed to combine the advantages of the use of springs
with those of frictional devices without the undesirable features of either, and to do
this there is employed in connection with a frictional connecting device a spring or
other elastic body which does not form the direct power transmitting connection but
which determines the frictional engagement so as to determine the power trans-
mitting value or capacity of the connection established thereby in accordance with
the load or with the power required.
It is preferred in transmitting power from one shaft to another to screw thread
the driven shaft and place therein an internally screw threaded nut and around the
shaft a spring is coiled or if the shaft is to run in either direction two springs are
used one on each side of the nut.
The nut is so arranged as will be explained that when the driving shaft begins to
turn, the nut turns on the driven shaft and so is screwed up against the spring until
it reaches a point at which the pressure of the spring is such as to cause the nut to
engage the screw thread with sufficient friction to turn the driven shaft. The power
is thus applied gradually and proportionately to the load and upon the stoppage of
the driving shaft the nut will run back under the spring pressure to its original
position. In electric railway cars the invention enables the armature of the
motor to make one or more revolutions before it engages with the axle to start
the car.
In the simplest form of the invention the travelling nut takes the form of a gear
wheel on the screw threaded driven shaft with a spring coiled on the shaft on each
side of it; and a wide pinion, on the driving shaft engages directly with this gear

page_text: wheel so that as soon as the driving shaft turns it causes the movement of said gear
wheel.
In another form the gear wheel on the driven shaft has a hollow cylindrical hub
surrounding the screw threaded part and inclosing the nut and springs, the nut
being keyed to the. interior of the hub. Thus when the driving shaft turns it
turns the hub which turns the nut and moves it along the shaft within the hub as
before.
With both these arrangements there is a permanent connection between the two
shafts, but in some cases it is desirable to so arrange the parts that the two shafts
may be entirely disconnected when the driving power is not required.
In one arrangement for this purpose 1 employ the hollow hub inclosing the nut
and springs as before, but I do not key the nut to the hub but leave it normally
disconnected therefrom. The nut in this case has cam faces and on each side of it
between it and the spring is placed a disc loose on the shaft but keyed to the hub,
each disc having a corresponding cam face. When the driving shaft is started, I,
by suitable means, move the nut up against one of the discs so that it engages there-
with, and the hub being turned by the driving shaft, the nut moves along up the
driven shaft until it engages therewith as before explained. When the shafts are
stopped the nut runs back again to its central position at which it is completely
disengaged from the disc so that the shafts are now disconnected. A light
spring is placed between the nut and each disc to assist the disengagement
thereof.
The moving of the nut against the disc may be done mechanically but it is
preferred to use an electrical device which may consist of wire coils wound on the
hub on each side of its middle point so that when current is passed through either
coil the nut is attracted in that direction.
In applying the invention to electric motors, these coils are so connected with
the circuit of the motor that when such circuit is closed these coils are placed in
circuit and caused to attract the nut.
In another arrangement two travelling nuts are employed one at each end of the
hub and with the spring between them and also between the two loose discs of which
there is one for each mut.
On the outside of the hub is placed a moveable part connected with the nuts
which when moved electrically or otherwise brings such nuts against their respective
discs and the turning of the shaft then moves one nut or the other according to the
direction of revolution toward the centre of the hub until it engages with and turns
the shaft.
In some cases a device such as constitutes the present invention is placed on
each of the two shafts so that on each shaft there is a moveable mut or body,
both of which move upon the application of power whereby the extent of motion
required and the space required for the apparatus are lessened.
Dated Lino m
Dafodring my 1800
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, Agents.
COMPLETE SPECIFICATION.
Improvements in Devices for Transmitting Power, and Especially for
Transmitting Power from Electric Motors used for the Propulsion
of Vehicles.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23, Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of the said inven-
tion, a communication to me from abroad by Edward Hibberd Johnson, of the
City of New York, United States of America, Electrician, and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement:-

page_text: The invention relates to devices for transmitting power or motion from a rotating
part or body to a part or body designed to be rotated thereby, or usually, from a
driving shaft to a driven shaft. Said invention was designed with especial reference
to the transmission of power from the armature of an electric motor to the axle of
It is however in its more essential
a railway car to be propelled by the motor.
features adapted for use in apparatus or machinery of any character in which power
is to be transmitted from one shaft to another. The main objects of the invention
are to produce a simple and effective device or apparatus in which the power trans-
mitting value or capacity of the connection between the two parts will be constantly
proportioned to the power required and which will enable the power to be applied
gradually in starting.
Another object which is especially useful in electric railway cars is to enable the
driving shaft to be readily thrown out of gear with the axle when the car is on a
down grade, or when for other reasons this is desirable.
Heretofore attempts have been made to apply power gradually and in proportion
to the load by means of springs connected between the driving and driven body
which were wound up or put under tension by the motion of the driving body until
finally they were enabled to move the driven body. Devices however which depend
on springs for directly transmitting power have practical defects which are well
known to mechanics. Devices which depend on the rubbing friction of two opposed
surfaces have also been employed, but such devices also have undesirable features.
In the present invention are combined the advantages which arise from the use of
an-intermediate-spring-and-those-which attend the employment of friction devices,
in such a manner as to avoid the objectionable features of each and this is
accomplished mainly by the use in connection with a frictional connecting device of
a compression spring or other yielding and elastic body which does not form the
direct medium for transmission of power, but which determines the frictional
engagement of the connecting device so as to determine the power transmitting
capacity or value of the connection established thereby in accordance with the load
or with the power required. It is preferred to make use of a part connected with
the driving shaft and movable so as to be brought into frictional connection with
the driven shaft and the elastic determining device is so placed that it opposes and
limits the movement of the said intermediate part and so determines the degree of
friction with which said intermediate part engages the driven shaft. It is preferred
to screw thread the driven shaft and make the said intermediate part a nut or other
internally screw threaded body travelling thereon, the elastic determining device
being preferably a compression spring coiled around the shaft so that the nut travels
against its pressure. Such nut is connected, in some cases permanently and in others
temporarily as will be explained with the driving shaft, so that by the movement of
the latter the nut is screwed up against the yielding stop or determining device
until it reaches a point at which the pressure of the latter is such as to cause the
nut to engage the screw thread on the shaft with sufficient friction to turn the
shaft; upon the stopping of the driving shaft the nut will run back under the elastic
pressure upon it, along the screw thread to its former position. It will be seen that
by the present invention the power is applied gradually and the value of the
frictional engagement and the amount of power transmitted are automatically
determined by the work to be done. In other words this result is accomplished
which is believed to be new. A moving and a motionless shaft is gradually inter-
locked with an engagement whose value is positively progressive until it equals the
It will be seen
work to be done and is afterward invariably proportional thereto.
also that the shaft may be automatically disconnected when the power is withdrawn,
and that in electric railway cars the use of the present invention enables the
armature of the motor to make one or more revolutions before it engages with the
axle to start the car, and when the car runs down hill the armature may be
disconnected so that only the wheels of the car will be in motion.
In the accompanying drawing I have mainly illustrated the present invention as

page_text: applied to electric railway cars but it will be evident that its uses are not
to that class of apparatus.
Figure 1. is a plan view of a portion of a street car truck provided with an
electric motor and with devices embodying my invention.
Figure 2. is a cross section of the cylinder containing the travelling nut on the
line 2, 2, of Figure 1.
Figure 2 an elevation of a somewhat modified arrangement.
Figure 3. a plan view of the truck and motor illustrating another form of the
present invention in which the nut is normally disconnected from the driving shaft:
Figure 4. a vertical longitudinal section of the cylinder and gear wheel in this.
form;
Figure 5. a cross section of the cylinder.
Figure 6 a longitudinal vertical section of the gear wheel and hub in a modified
arrangement in which the temporary connection between the nut and the driving-
shaft is made by friction.
Figure 7. a cross section on the line 7, 7, of Figure 6 and
Figure 8 is a view illustrating the modified construction in which both shafts are
provided with flexible power transmitting devices.
Referring first to Figures 1 and 2, A A are car wheels, B is the axle connecting
then and C is a counter shaft connected with axle B by gear wheels D D¹. E is
the armature shaft of an electric motor F. Upon the armature shaft E is a pinion G
which engages with a toothed gear wheel H. The hub on which the said gear
wheel His fixed is a hollow cylinder sleeved on the counter shaft C. The
portion of said countershaft within said cylinder is formed with a screw thread K.
The pitch of the screw should in all cases be one of such length as to allow the
elastic stop to readily reverse the apparatus and force the nut back on the thread.
The exact pitch necessary for this is dependent on various conditions such as the
situation in which the device is placed, the amount of movement which may be
allowed to the nut, the strength of the spring &c.
I is the nut which forms the
intermediate connecting device, such nut being threaded on the shaft C and being
provided with lugs a, which enter internal slots in the cylinder I.
The operation of these devices is as follows:- When the car is in the state of
rest, if current is applied to the motor, the pinion G turns the wheel H and
cylinder . The nut L being in positive engagement with the cylinder turns with
it and is therefore screwed up in one direction or the other according to the way
the armature is running along the shaft and against the spring M or M until it
reaches a point where the compression of the spring is such as to hold it back
against the screw thread with such friction that its turning movement is com-
municated to the countershaft and the same turns and starts the car at first slowly
and with increasing speed as the compression of the spring increases until it reaches
such a point that the nut will move no further, such point being dependent on the
load or the amount of resistance to starting which has to be overcome.
The difficulty which has constantly arisen in the operation of electric railway
cars is that while the power required to start the car is greater than that required
when in motion the electrical equipment is then least effective and must therefore
for the purpose of starting be largely in excess of what is subsequently required
and even this provision is not always sufficient to avoid injury to the motor by the
excessive current which passes through the armature while the same is at a stand-
still and is developing no counter electro-motive force. It will be readily seen that
these difficulties are materially lessened by the use of the apparatus just described,
since the load is brought gradually on the armature by the gradual compression of
the spring and the armature has time to make one or more revolutions and to begin
to develop its counter electro-motive force before the load is placed on it.
While the car is running the engagement of the shafts alters with variations in
the load so that the value of such engagement and the power transmitted change
with the power required that is to say the point at which the nut engages with the
г

page_text: screw thread sufficiently to turn the shaft will depend on the load at the time of
starting and if the load afterwards increases the nut will run further up on the
screw thread or if the load decreases it will be relieved and will run back toward
the centre.
In the arrangement shown in Fig. 24 the cylindrical hub is omitted and the gear
wheel H is threaded directly upon the shaft and placed between the springs M M'
which are coiled on the shaft between stationary collars. The operation will be
readily seen. When the wheel H begins to turn it runs upon the screw thread
against the spring until it reaches a point where it will turn the shaft. The pinion G
is made long enough to permit the movement of the wheel H.
In the forms of the invention so far described the nut is always in engagement
with the cylinder and the armature therefor is always in connection with the
axle. In order that when necessary or desirable the armature may be automatically
disconnected from the axle so that the axle alone will revolve there are added to
the simple construction shown in Figure 1. certain other devices illustrated in the
remaining figures of the drawing, which I shall now describe.
Figures 34 and 5 illustrate a device in which the nut is normally out of engage-
ment with the cylinder and is moved bodily into engagement therewith by electro
magnetic attraction. The wheels A axle B countershaft C motor Farmature
shaft E pinion G and gear wheel H are arranged substantially as before described
but I have in this case shown the power transmitting device on the driving axle
instead of on the countershaft. It is evident that either situation may be selected
for this device according to the requirements of any particular use.
In Figure 1 the device is shown on the counter shaft but the same device can:
evidently be placed-on-the-axle-and-the-different device shown in Figure-3-may
evidently be used as well on the counter shaft. Neither of course is the use of a
counter shaft in any way essential to the invention although I have illustrated its
use because it is preferably employed in electric railway motors. Referring to
Figures 34 and 5 the axle B is formed with a screw thread N under the cylinder, I,
which is loose on the axle and within said cylinder are compression springs M M'.
Threaded on the shaft of the axle and situated normally at the middle of the
cylinder I, as shown in Figure 4, is a nut O which is formed with cam surfaces
adapted to engage with corresponding surfaces on the inner faces of discs P, P¹,
situated one on each side of the nut O held away from said nut by light springs, c,
and provided with lugs d which enter internal slots d' in the cylinder.
The cam surfaces of disc P are shown at 6 in Figure 5 and those of the nut O are
of a similar character so as to engage therewith. The nut O is of less diameter
than the cylinder so that it does not come into contact therewith. The discs P
and P are loose on the screw threaded axle. The cylinder forms the hub of the
gear wheel D which engages the pinion D¹. Upon the hub I on each side of the
gear wheel D is placed a spool wound with a wire core Q or Q. Such spools may
be supported by a bracket R from the motor bearings as illustrated in Figure 3, or
in any suitable way.
These wire coils are connected with a suitable source of electric current which
in the case of an electric railway car is preferably the source which supplies current
to the motor. The source of supply is indicated by the conductors 1 and 2 with
which the coils QQ are connected by wires 3. 4. and 5 through the switch S. The
switch shown is a simple form of switch which may be used with electric railways
for the purpose of opening and closing the motor circuit and for the purposes of the
present invention it is provided with additional connections with the coils QQ' so
that when the handle is thrown to one side or the other to start the motor in one
direction or the other, it at the same time closes the circuit to either the coil Q
or Q The nut O, being made of magnetic material, when cither of the coils is
energized, such nut is attracted towards such coil and is therefore brought into
engagement with the disc P and P' as the case may be. The cylinder I having at
this time begun to revolve because of the application of current to the motor at
the same time as to the coil, as soon as the cam surfaces of O and P engage,

page_text: the nut O begins to turn with the cylinder and is therefore screwed up along the
shaft pushing the disc P and compressing the spring M in front of it, until as
in the previous instance, the spring M becomes so far compressed as to force the
nut against the screw thread with sufficient friction to turn the shaft.
When the current is removed from the motor the nut is run back along the shaft
as before explained being followed by the disc P until such disc reaches the ends of
the slots when the springs remove the nat O from the disc P and so entirely
disconnect the armature shaft from the axle, and the parts remain in this situation
until the current is again applied and the coil Q or Qi attracts the nut against one
of the loose discs.
It will be seen that all the operations described with reference to Figure 1. are
performed by the device in Figures 3 and 4 but in addition the latter device enables
the armature to be thrown out of gear with the axle when the car is on a down
grade. At such time, current being shut off from the motor the force which tends
to keep the nut O screwed up against the spring is removed and the spring therefore
forces the nut back over the long pitched thread to its central position with the.
result already explained.
In the arrangement shown in Figures 6 and 7 the manner of giving the nut its
initial movement which starts it upon the screw thread is a different one from that
just described. Instead of moving the nut bodily into engagement with the cylinder
it is made to turn with the cylinder by a temporarily applied friction device. Such
a device may be operated by hand or in any suitable way. It is shown as operated
electrically by the attraction of the field magnet of the motor with which the device
is connected.
In Figures 6 and 7 the device is shown applied to a stationary motor T
transmitting power to the shaft B which may be the shaft of any driven machine or
apparatus. The cylinder I is placed over the screw threaded part of the shaft B
and forms the hub of the gear wheel D which engages with the pinion D' on the
armature shaft E. The device shown in Figure 6 differs in many respects from
those previously described. Near each end of the screw thread is placed a threaded
nut and two loose discs 9 g₁ are placed in proximity to said nuts. At the
middle part of the cylinder between the discs gg is placed the compression spring h.
It is preferred to employ two springs, one within the other as shown. Light
springs are placed between the screw threaded nuts and the loose discs as before.
Between cach nut and the end of the cylinder is placed loosely on the shaft an
internally bevelled collar. The collar has extending from it pins & which pass
through slots in the cylinder, and are attached to sliding collar on the outside of
the cylinder. The collar is normally in contact with a similar collar they being
held together by springs m. The collar also has pins extending through slots in
the cylinder into the interior thereof, such pins being attached to strips which
extend inside of the cylinder and are attached to the internally bevelled collar i at
the other end of the cylinder.
which
Upon the motor T in proximity to the poles thereof is a magnetic bar or plate n
from which a bell crank o extends connected by a link with a forked arm
P,
carries wedges each consisting of a bevelled roller adapted to enter between the
collars and to force the same apart. The edges are normally held between
said collars by a spring s but are withdrawn therefrom by the attraction of the.
magnet of the motor T for the magnetic.barn.
.
As shown the parts are in operation; when they are at rest and the wedge is
between the collars 1, 7, the inner collar is out of contact with the mut f' and so is
the collar i out of contact with the nut f, being pushed away from it by the strip /¹.
When current is placed on the motor the cylinder I begins to revolve and at the
same time the wedge is withdrawn so that the collars are brought together by
the springs m and the double collars i are brought into frictional engagement with.
the bevelled edges of the nuts f₁ respectively whereupon both said nuts begin to
turn with the cylinder and one or the other of them, according to the way in which
the shaft is turned, will be screwed up along the shaft so it will engage with the
1

page_text: disc g or g' after which it will continue to run up the shaft and compress the spring
until it engages with the shaft and turns the same as already explained. As shown
the shaft is turning in the direction indicated by the arrow in Figure 6, which
screws the nut f up toward the centre of the cylinder and keeps the nut f¹ at the
end of the cylinder. If the motor was started the other way these conditions would
be reversed. When the current is taken off the motor the nut will run back but
will not come into contact with the collar because the wedges will be forced
into place again and keep said collars so near the end of the cylinder that the hub
of the nut will strike the end of the cylinder before the mut reaches the collar.
In Figure 8 is shown the simple form of the invention shown in Figure 2ª to.
illustrate the application of the present invention to both shafts.
The gear
wheel H is threaded on the driven shaft between the springs M M';;
the pinion G is threaded on the driving shaft between springs M² M³. When the
driving shaft starts, the pinion G being prevented at first from turning by its
engagement with the motionless driven shaft will be screwed up against one of the
springs until it engages the shaft with such force as to start the wheel F which will
then be screwed along its shaft until it also turns the same.
It will be seen that the longitudinal movement is thus divided between the two
shafts so that the movement on any one shaft is less than that which would otherwise.
be required.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The apparatus for transmitting power and motion from one shaft to another,.
in which a movable body is moved along one shaft, by the motion of the other,
against the pressure of an elastic cushion, until it reaches a point where it engages.
with the shaft on which it is placed, so as to connect the two shafts mechanically
together, substantially as hereinbefore described.
2. The combination of the driving shaft, the screw threaded driven shaft, the nut.
on the driven shaft connected permanently or temporarily with the driving shaft
and the springs opposing the movement of the nut on the screw thread substantially
as hereinbefore described.
3. The electrical devices for moving the nut temporarily into connection with the
driving shaft substantially as hereinbefore described.
4. The application of the described device to electric motors used for propelling.
vehicles on railways substantially as hereinbefore described.
Dated this 28th day of February 1891.
Dated this 28th day of February 1891.
B. J. D. MILL.
By Harris & Mills,
23, Southampton Buildings, London, Agents.