Improvements in Devices for Transmitting Power, the same being specially adapted for use with Electric Motors Propelling Cars or Vehicles.
Year: 1891

page_text: Date of Application, 23rd Mar., 1891
Complete Specification Left, 10th Nov., 1891-Accepted, 12th Dec., 1891
PROVISIONAL SPECIFICATION.
Improvements in Devices for Transmitting Power, the same being
specially adapted for use with Electric Motors Propelling Cars
or Vehicles.
1, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of this invention,
a communication to me from Edward H. Johnson, of the City, County and State
of New York, United States of America, Electrician, to be as follows:-
This invention relates especially to improvements on the devices and apparatus
described in my Provisional Specifications Nos. 14,609 and 146094, both dated
September 16, 1890, in which are set forth a device consisting of two screw
threaded sleeves on a car axle situated, with relation to a friction device, so that
by movement of the axle in either direction such friction device is made to produce
a frictional connection with the car wheel sufficient to start the car; and also the
providing of such an apparatus with stops arranged with relation to the safe
capacity of the motor, so that the frictional engagement cannot increase beyond
such safe capacity.
Where screw threaded sleeves are employed in this manner, it is necessary to
make the screw threads of a long pitch so that they can return readily to their
normal position; it is also necessary, in electric railway cars, to permit the motor,
when the car is started, to make one or more revolutions before its power is applied
to the wheel. To do this with a long pitched screw thread required that the
sleeves should have considerable travel, and in view of the limited space for the
apparatus in railway cars, this objection was one which it is found desirable to
obviate. To this end I use, according to the present invention, what I term a
compound nut, consisting of any required number of concentric cylinders threaded
one upon another. The threads on the cylinders are made of long pitch, each
cylinder being provided with several separate threads extending from one end to
the other.
In applying this device to a car, according to one method, I place on the axle, a
sleeve, extending from one wheel to the other, which has internal shoulders forming
bearings on the axle for the sleeve. At each end of the sleeve it has an external
flange, outside of which the car wheel is fixed on the axle. Each car wheel has a
hub extending inwardly over the axle, which may be made in sections secured to
the wheel by bolts so as to be removable. Inside the hub is a split bevelled ring,
and adjacent to this on the sleeve, is a bevelled ring which forms a wedge to enter
the split ring and force it out against the hub. The parts of the split ring are
keyed to the flange on the end of the sleeve so that they cannot turn. A spiral
spring is coiled on the sleeve so as to press against the wedging ring. Each of the
two wheels is provided with these devices, and between the two springs on the sleeve
is placed the compound nut. A cylinder having an external screw thread is
attached to the sleeve on the axle by a spline or feather; outside of this is another
cylinder, and outside of that still another, these two being each screw threaded both
internally and externally; then over the whole is a fourth cylinder with an internal
screw thread. Of course the number of cylinders in the compound nut may be
increased, but four is sufficient for illustration, and, in most cases, for practical
An increase in the number of concentric cylinders has the result of increasing
the number of free revolutions allowed to the motor armature.
use.

page_text: In order to limit the travel of the cylinders on each other with reference to the
safe capacity of the apparatus, one of the channels of each external screw thread
is provided with a groove extending from one end of the thread nearly to the other
end, and the corresponding rib of each internal screw thread is provided with a pir
projecting into the groove; thus when they are turned in one direction, the pin wil
travel in the groove until it reaches the end and further movement in that direction
will be stopped. Another channel of each external screw thread has a groove
whose open end is at the same end of the cylinder as the closed end of the first
mentioned groove and which terminates near the end of the cylinder at which the
first groove is open. Pins on the corresponding ribs enter these grooves also
This provides for movement of the sleeves in the opposite direction from before,
since the first pin and groove will not in this case limit the movement but the
second set will. At each end of the compound nut a sliding collar is placed on the
sleeve, having rollers on its surface bearing against the ends of the cylinders of
the nut to let them turn casily. The springs before referred to press against the
other sides of these sliding collars.
The motor or motors which propel the vehicle may be arranged in any suitable
and convenient way, and their armatures are geared or mechanically connected
with the external cylinder of the compound nut. This outer cylinder may be
formed with a sprocket wheel and a sprocket chain may extend from this to the
armature shaft, or other forms of gearing may be employed. Both axles of the
truck or car may be provided with the described devices.
1.
When the motor is started, the motion first turns the outer cylinder of the com-
pound nut, and this will cause half of the cylinders to be screwed out in one
direction and the other half in the other direction, whichever way the motor runs,
half the cylinders will go in one direction and half in the other direction; the
turning of these cylinders at first does not affect the car wheels, but it compresses
the springs and this causes the wedging rings to be pushed in between the segments
of the split collars and wedge them out against the hubs of the wheels so as to
apply friction and turn the wheels. The amount of friction will depend on the
degree to which the springs are compressed, and this in turn depends upon the
extent of movement of the compound nut, which is itself dependent on the load to
be started by the motor; the greater the load, the greater will be the movement
necessary to compress the springs sufficiently to give the necessary friction to turn
the wheels.
The limiting stops in the screw threads prevent the motor from exceeding its safe
capacity. These stops are so situated that if the load is too heavy for the motor
to start, the stops will engage each other before the point in the movement of the
compound nut at which the safe capacity of the motor is attained, so that at this
point any further increase of friction is prevented and the friction surfaces will slip
on each other and the motor will start and will continue to run, developing its full
capacity but not exceeding the same, until relieved. When the current is cut off
from the motor, the springs force the nut cylinders back to their normal position so
as to remove the friction and let the car stop. In forcing back the nut cylinders,
the spring causes them to turn in the opposite way from that in which they have
been turned by the motor, and so tends to assist in stopping the motor:
By using the sleeve on the axle, the wheels of the car are enabled to be fixed 'on
the axle, instead of being loose as before proposed, since such sleeve forms the
necessary support, independent of the wheels, for the actuating nut.
I, however, may employ the compound nut without the sleeve, and in this case I
have the wheels loose on the axle, they being placed between fixed collars on the
axle. In this case I provide the wheels with hubs extending over the axle, with
the split friction rings, the bevelled wedging rings, and the springs, as before, and
the operation is as I have explained it.
It will be seen that by the use of the compound nut, the number of revolutions
required to compress the spring enough to furnish the necessary friction is increased,
and I am thus enabled to obtain a greater number of revolutions without shortening

page_text: the pitch of the screw threads and without increasing the lateral travel of the
apparatus.
Doted this 23rd day of March 1891.
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in Devices for Transmitting Power, the same being
specially adapted for use with Electric Motors Propelling Cars
or Vehicles.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings in the
County of Middlesex, Patent Agent, do hereby declare the nature of this invention,
a communication to me by Edward Hibbard Johnson, of the City, County and
State 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 :-
This invention relates especially to improvements on the devices and apparatus
described in the Specifications of Patents Nos. 14,609 and 146094, both dated
September 16, 1890, in which are set forth a device consisting of two screw-
threaded sleeves on a car axle situated, with relation to a friction device, so that by
movement of the axle in either direction such friction device is made to produce a
frictional connection with the car wheel sufficient to start the car; and also the
providing of such an apparatus with stops arranged with relation to the safe
capacity of the motor, so that the frictional engagement cannot increase, beyond
such safe capacity.
Where screw-threaded sleeves are employed in this manner, it is necessary. to
make the screw threads of a long pitch so that they can return readily to their
normal position; it is also necessary, in electric railway cars, to permit the motor,
when the car is started, to make one or more revolutions before its power is applied
to the wheel. To do this with a long pitched screw-thread required that the sleeves
should have considerable travel, and in view of the limited space for the apparatus
in railway cars this objection was one which it is found desirable to obviate. To
this end I use according to the present invention what I term a compound nut
consisting of any required number of concentric cylinders threaded one upon
another. The threads on the cylinders are made of long pitch, each cylinder being
provided with several separate threads extending from one end to the other.
The invention is illustrated in the accompanying drawing
-
Figure 1, is a top view of a street car truck embodying all the features of the
invention.
Figure 2, a longitudinal section of the compound nut.
Figure 3, a side elevation of the same with the sleeves projecting one from
another.
Figure 4, an end view of the same.
Figure 5, a face view of the friction ring which I prefer to use.
Figure 6, a section on a larger scale than Figure 1 of the perforated arrangement
of the car wheel and friction devices, and
Figure 7, a section of the sleeve which encloses the shaft in this arrangement.
In Figure 1, I have shown upon the same truck two different forms of friction
devices. That which I prefer to employ is shown at the right hand end of the
sheet. It will be understood that in practice the same form of friction device will
preferably be used at both ends of the car, but for convenience of illustration I have
shown the two different forms on the same car.
Considering then the device shown at the right hand end of Figure 1, the axle A

page_text: is provided with a sleeve B extending from one end to the other thereof between
the wheels, the sleeve having internal shoulders a (Figure 7) which form bearings
for said sleeve, the sleeve not being in contact with the axle at other points. At
each end of the sleeve B it is formed or provided with a flange b, outside of which
is fixed upon the axle the car wheel C. The car wheel has attached to it an
inwardly extending hub or ring D., this being preferably made in sections secured
to the wheel by bolts c so as to be readily removable if desired. Placed loosely
upon the outside of the sleeve B is a bevelled ring d, which forms a wedge entering
between the parts of the sectional friction ring e. As shown in Figure 5, this is a
split ring made in three parts and bevelled on its inner edge. Each of the three
parts of which the ring is made is provided with a rib fon its outer side, and these
ribs enter slots in the flange b so that the split ring e is prevented from turning, but
its parts are enabled to move outwardly against the hub D when the wedged is
forced against their inner bevelled side."
Upon the sleeve B is coiled a spiral spring E. It will be understood that at
the other end of the axle A and sleeve B'there is a similar device for communicating
motion to the wheel C¹; D' is the hub secured to said wheel, and E' the spiral
spring at that end of the axle.
At the middle portion of the axle between the springs E and E¹ is placed what
I term the "compound nut "N' and which is shown in detail in Figures 2, 3 and 4.
For simplicity of illustration the sleeve B is not shown in these figures, but the
device is shown as placed directly on the axle, as I sometimes employ it in practice
and as I shall presently explain. Keyed to the axle A (or in the other case to the
sleeve B) is a sleeve g having an external screw thread.
Outside of this is a
sleeve h, and outside of this a sleeve i, the sleeves h, i being each screw-threaded
both internally and externally.
External to the sleeve i is an outer sleeve k with an internal screw thread. As is
indicated in Figure 3, the screw threads are not continuous but each one is made
up of a number of separate channels or ribs, each extending from one end of the
sleeve to the other.
In order to limit the travel of the sleeves on each other so as to limit the degree
of frictional engagement with reference to the safe capacity of the apparatus, one
of the channels of each external screw-thread is provided with a slot extending
from one end of the thread nearly to the other end, and the corresponding rib of
each internal screw-thread is provided with a pin projecting into the said slot;
thus when they are turned in one direction the pin will travel in the slot until it
reaches the end thereof and further movement in that direction will be stopped.
Another channel of each external screw-thread is provided with a slot 12 whose
open end is at the same end of the sleeve as the closed end of the slot and which
terminates near the end of the sleeve at which the slot is open; pins 13 enter the
slots 12. This provides for movement of the sleeves in the opposite direction from
before, since the first pin and slot will not in this case limit the movement, but the
second set will. The stop pins are screws passing through holes in the sleeves, so
that they may be inserted after the sleeves are put together.
At each end of the compound nut there is placed upon the shaft a sliding collar F
or F, and these collars have face grooves in which are set at intervals rollers n, n
whose axis is at right angles to the shaft and is formed by pins m extending from
the periphery of the collar toward the shaft.
The other axle A¹ of the vehicle being provided with similar devices to those
just described, a suitable arrangement for the motors to propel the vehicle is as
follows: G is the upper frame of the truck which is supported by springs from the
axles and which rigidly carries the car body. Extending across this frame at a
sufficient distance below it to provide room for the motors are two cross beams H. Ho
The motors shown have field magnets of the Siemens type and are rigidly secured
to the cross beams H by means of bolts o passing through ribs projecting from their
yokes at each end.
The armatures I, I' are placed upon a common armature shaft K having bearings

page_text: at each end (extending from the field magnets) these bearings being readily
accessible from the sides of the cars. The commutators being placed at the inner
ends of the armatures are close together so that they can be inspected simul-
taneously by opening a single trap-door in the bottom of the car. Between the
two commutators on the shaft K are mounted two sprocket wheels p, p'; from the
sprocket wheel p a sprocket chain L extends to a larger sprocket wheel M' fixed
upon the outer sleeve of the compound nut N, and from the sprocket wheel pla
sprocket chain L¹ extends to a sprocket wheel M¹ on the outer sleeve of the
compound nut N'.
i
It will be seen that when the two motors are started the revolution of the
armature shaft K will be such as to turn both axles in the same direction and thus
to propel the car. Referring to the device of Figure 6 and the right-hand end of
Figure 1, the motion first turns the outer sleeve of the compound nut, and the effect
of the application of power will be to cause the sleeves k, h to be screwed up in one
direction, say against the collar F', while the sleeves g, i will be screwed out in the
other direction and against the collar F. The rollers n are provided for the purpose
of preventing excessive friction of the ends of the sleeves against the collars so as
to let the sleeves turn easily. If the power is applied to start the car in the other
direction, the motion of the two pairs of sleeves will be reversed, the sleeves
being forced against the collar F and the sleeves h, k against the collar F. The
turning of the sleeve B of course does not affect the wheels. In either case the
result is, to compress the springs E, E'. The pressure of the springs E, E' causes
the wedges d to be pushed in between the segments of the split collars e and wedges
these segments out against the hubs D so as to apply friction to the hubs and turn
the wheels. The amount of friction will of course depend on the degree to
which the springs are compressed, and this in turn depends upon the extent of
movement of the compound nut, which is itself dependent on the load to be started
by the motor; the greater the load, the greater will be the movement necessary to
compress the springs with sufficient force to give the necessary friction to turn the
wheels and axle. The provision of the sleeve B surrounding the axle permits the
wheels to be fixed upon the latter instead of being loose thereon, since such sleeve
forms the necessary support independent of the wheels for the actuating nut.
In
When the current is cut off from the motors and power therefore ceases to be
applied to the external sleeves of the compound nuts, the pressure which has tended
to keep the springs compressed being thus removed, such springs force the nut
sleeves back along their long-pitch screw-threads to their normal position so that
the friction is removed from the wheels and the car is allowed to stop, or, in running
on a down grade, the wheels may continue to run without running the motor.
forcing back the nut sections, the spring causes the same to turn in the opposite
way from that in which they had been previously turned by the motors, and
this tends to produce a reversal of the motors which assists in stopping the same.
The form of friction devices shown at the left hand end of Figure 1 of the
drawing differs somewhat from that heretofore described, although the general
operation is the same.
In this arrangement the sleeve B, which in the form already described constitutes
the shaft of the compound nut, is not used, but the wheel C2 is loose on the axle A',
being placed thereon between fixed collars r, b. The hub D' of said wheel extends
out over the shaft as before, while upon the shaft is placed the bevelled collar d to
act as a wedge. In operation the wedge d forces the segments of the collar o out
against the bub D' as has already been described.
It is considered desirable in electric railway cars to provide each car with two
motors so that in case of accident to the armature of one of them the other may be
made use of. It is for this reason that I provide two motors with my arrangement,
but I so connect them, they being provided with a common armature shaft as we
have seen, that in practice they operate together as one motor, although they are
geared to different axles. Instead of a continuous shaft however, the shafts of the
two armatures may be separated at the centre and normally joined by a suitable

page_text: clutch, so that in case of accident to one armature, the other may if desired be
disconnected and run separately. An additional bearing is in this case provided for
the inner ends of the armature shafts. By employing sprocket gearing the
horizontal motion of the nuts on the axles is allowed for and also such vertical
movements of the car body on its springs as may occur. and I am thus enabled to
carry the motors wholly on the truck frame instead of having to carry the
same upon rigid frames supported upon the axles as has hitherto been found
necessary.
The pins and slots in the screw threads, as already mentioned, form limiting stops
to prevent the safe capacity of the motor from being exceeded. This is an
important feature of my invention. When the load on the car is too great for the
motor, starting from a state of rest and having to overcome the inertia of the car,
to move, without taking so much current as to endanger it, then, if these stops are
not provided, the motor will continue to cause the frictional engagement with the
wheels to increase and the motor being unable to revolve freely will probably be
destroyed by the excess of current.
The limiting stops are however placed at such points that before the motor can
be exposed to danger, the motion of the screw threaded sleeves is absolutely
stopped and so the frictional engagement can increase no further, and therefore the
power of the motor will be expended in turning the friction surfaces against each
other until the motor attains such efficiency as will enable it to start the car without
danger, or if the load is too heavy for this even, until it is lightened or relief is
obtained in some other way.
Instead of proportioning the stops to the safe capacity of the motor, they may in
the case of cars or vehicles in which the current is furnished by accumulators or
secondary batteries, be so proportioned as to prevent the batteries being called
upon for a greater amount of current than they are designed to furnish. A serious
obstacle to the use of accumulators for propelling, railway cars, has been the bending
of the plates and the consequent rapid deterioration due to the excessive demand
made upon them in starting the car.
In other cases the provision of stops preventing increase of frictional engage-
ment beyond a predetermined point might be used to prevent excessive strain or
injury to mechanical portions of apparatus.
By employing the threaded sleeve on the shaft for moving the friction devices
into engagement, the result is obtained that no matter which way the motor runs,
the movement into frictional engagement will result. This could be accomplished
with only two sleeves, but by multiplying the number of sleeves I am enabled to
increase the number of free revolutions allowed to the armature before its power
applied to the wheels, without increasing the space required for the apparatus. In
order that the sleeves shall return readily to their normal position when the
application of power is removed, the screw threads must be of long pitch; but with
a long pitched screw-thread, if there were only two sleeves, they would require
considerable length of travel, and in view of the limited space for the apparatus in
street cars, this is undesirable. I therefore employ my
compound nut in which
the number of sleeves is multiplied and as each sleeve gives a part of the total
movement, the number of free revolutions which the motor can make is increased
while the space required on the axle for the sleeves to move is not correspondingly
greater. It is evident that the number of concentric sleeves can be increased, to
any convenient or desired extent.
66
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. The combination of a friction device for transmitting power and motion from
an electric motor to the wheels of a vehicle, the same being so connected with the
motor that the movement of the motor moves it into increasing frictional engage-
ment, a spring opposing such movement, and a stop or limiting device positively

page_text: limiting the degree of frictional engagement with relation to the safe capacity of
the apparatus, substantially as hereinbefore described.
2. The "compound nut for moving the friction devices into engagement, the
same consisting of several screw threaded sleeves, threaded one upon another, and
each having several distinct threads of long pitch, said sleeves being separated from
the friction devices by springs and one of said sleeves being connected with the
propelling motor, so that by the revolution of said motor the friction devices are
moved into engagement, substantially as hereinbefore described.
Dated November 10th 1901.
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, Agents.