U.S. patent number RE29,994 [Application Number 05/847,616] was granted by the patent office on 1979-05-15 for electric traction transportation system with storage battery powered vehicles and fast recharge at the vehicle stops.
Invention is credited to Oscar Bossi.
United States Patent |
RE29,994 |
Bossi |
May 15, 1979 |
**Please see images for:
( Certificate of Correction ) ** |
Electric traction transportation system with storage battery
powered vehicles and fast recharge at the vehicle stops
Abstract
An urban mass transportation system is disclosed which makes use
of storage battery powered vehicles. In view of the specific use
which implies preestablished routing of the vehicles and
preestablished stops at frequent intervals, the capacity of the
batteries installed in each vehicle is commensurate to the
capability of running for a limited distance. The vehicles are
further provided with contact means, such as trolleys, for
performing a fast recharge of the batteries at the stop stations,
without removing the batteries. The stop stations are equipped with
devices mating with the contact means and suitable for allowing a
fast recharge. Electrical power is taken from an electrical
distribution network independently from the routing of the
vehicles.
Inventors: |
Bossi; Oscar (Milan 20145,
IT) |
Family
ID: |
26327524 |
Appl.
No.: |
05/847,616 |
Filed: |
November 1, 1977 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
442881 |
Feb 15, 1974 |
03955657 |
May 11, 1976 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Feb 15, 1973 [IT] |
|
|
20427 A/73 |
|
Current U.S.
Class: |
191/2; 191/29R;
320/109; 191/1R |
Current CPC
Class: |
B60L
53/14 (20190201); B60L 53/11 (20190201); B60M
7/003 (20130101); B60L 50/53 (20190201); B60L
50/60 (20190201); B60L 53/32 (20190201); Y02T
10/70 (20130101); B60L 2200/18 (20130101); Y02T
90/128 (20130101); Y02T 10/7072 (20130101); Y02T
10/7005 (20130101); Y02T 90/14 (20130101); Y02T
90/12 (20130101); Y02T 90/121 (20130101) |
Current International
Class: |
B60L
11/18 (20060101); B60M 7/00 (20060101); B60L
001/00 () |
Field of
Search: |
;320/20
;191/1R,2,3,4,12R,29R,22R,45 R-50/ |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blix; Trygve M.
Assistant Examiner: Keen; D. W.
Attorney, Agent or Firm: Field; Milton M.
Claims
That which is claimed is:
1. A vehicle for an electrical traction passenger transportation
network having a plurality of stop stations for loading and
unloading passengers, said stop stations being other than
terminals, at least some of said stop stations being recharge stop
stations provided with contact means for connecting a vehicle to an
electric power line, and stretches between successive recharge stop
stations, said vehicle stopping a relatively short stop time of the
order of tens of seconds, normally not exceeding 1 minute, at each
recharge stop station and consuming an amount of energy while
running each stretch in between successive recharge stop stations,
said vehicle comprising:
electric motor traction means;
storage battery means having a storage capacity sufficient to store
the maximum amount of energy required to drive said vehicle over a
stretch between successive recharge stop stations, said battery
means having a nominal loading current; and
circuit means, including fast connection means for connecting said
storage battery means to said contact means at a recharge stop
station with a connection time permitting fast recharging of said
battery means for substantially all of said stop time, for
providing said battery means with fast recharging current from said
power line which is of the order of several tens times the
magnitude of said nominal current, including as much as the order
of 100 times said nominal current, and of sufficient magnitude that
said maximum amount of energy will be stored in said battery means
during said relatively short stop time.
2. An electric traction transportation system, comprising:
at least one vehicle as claimed in claim 1; and
a plurality of said stop stations, at least some of which are said
recharge stop stations provided with said contact means for
cooperating with said fast connection means for connecting said
vehicle to said electric power line.
3. An electrical traction transportation system as claimed in claim
2, wherein said contact means comprises an aerial feeding bar and a
ground feeding plate.
4. A vehicle as claimed in claim 1, further comprising means for
automatically connecting said fast connection means to said contact
means at the recharge stop stations.
5. A vehicle as recited in claim 1, wherein said fast connection
means operates to connect said vehicle to said contact means while
said vehicle is coming to a stop and to disconnect said vehicle
from said contact means after said vehicle starts into motion so
that all of said stop time and two short movement intervals are
available for charging said battery means.
6. A vehicle as recited in claim 1, wherein said contact means
comprises an overhead contact bar and a ground contact plate and
said fast connection means includes a trolley for contacting said
overhead contact bar and means responsive to engagement of said
trolley with said overhead contact bar for lowering into contact
with said contact plate.
7. A method of operating an urban mass passenger transportation
system including a plurality of electric traction vehicles, each
vehicle having battery means and a plurality of recharge stop
stations for loading and unloading passengers, said stop stations
being other than terminals and being separated by stretches, each
recharge stop station having contact means for connecting one of
said vehicles to an electric power line, comprising the steps
of:
energizing one of said vehicles from the energy stored in said
battery means for movement along one of said stretches between two
of said recharge stop stations;
rapidly connecting said vehicle to said contact means as it stops
at a stop station; and
recharging said battery means with at least the same energy
consumed while driving said vehicle over the preceding stretch with
a fast recharge operation over a relatively short stop time of the
order of tens of seconds, normally not exceeding one minute, while
said vehicle is stopped at said stop station by drawing recharging
current which is of the order of several tens times the nominal
loading current of said battery means, including as much as the
order of 100 times said nominal loading current, from said power
line.
Description
BACKGROUND OF THE INVENTION
The instant invention deals with land transportation means in which
such means operates over relatively short stretches between one
stop and the following one. In particular, this invention deals
with mass transportation systems, such as the urban transportation
systems, where many intermediate stops at determined places must be
effected. Considering, by way of example, urban transportation
means, which practically have not been subjected to changes in the
last half century, it is possible to distinguish: transportation
means having a rigidly constrained path, which derive from the
urbanized railway, such as trams (trolley-cars), underground
vehicles, monorail vehicles, and like; transportation means having
a free path, such as motorbuses; and transportation means having a
semi-constrained path, such as trolley-buses.
Of these transportation means, the tram is declining in usage by
reason of its rigidly constrained path which makes it unable to
overcome any hindrance on its way, missing the agility and
flexibility which is required in the modern traffic. The motorbus,
which is mainly diesel motor powdered, is the most common and
widespread transportation means by reason of its path freedom.
However, its propulsive system has a serious disadvantage: air
pollution caused by exhaust gases of internal combustion engines.
In addition, the pollution is increased by the fact that during the
service the engine remains in operation even at the stops. Other
disadvantages are the wasting of energy due to the low efficiency
of the engine and its noise. The trolley-bus, being free from rail
constraints, thus not having a rigidly constrained path, was
expected to replace trolley cars as well as motorbuses. In fact, it
has the non-polluting, noiseless, and nimbleness advantages of
electric traction. In spite of these advantages, use of the trolley
bus has not spread as expected due to other disadvantages, such as:
cost and complexity in building up the two pole electrical aerial
power line; very high maintenance cost of the aerial lines; the
impossibility for the vehicle to deviate to paths which are not
provided with electrical power lines; and the limited transverse
freedom allowed by the trolley, which is subject to disjunction
from the line, if the trolley-bus, in order to avoid encumbrances,
deviates transversely too much .[.will.]. .Iadd.with
.Iaddend.respect to the electrical line.
As a consequence, actual research projects are devoted to the
development of urban transportation means free from any path
constraint (power lines) or rigid way constraint (rails), as it is
for the motorbus, and, however, noise and pollution exempt as it is
for electrically powered vehicles. Many solutions have been
proposed and many attempts made without obtaining a satisfactory
result. Storage battery powered vehicles have been developed which
are believed to be the best way to solve the problems of urban
traffic. At the present day, however, they are not used because the
energy sources available have a serious limitation: the very low
value of specific energy stored per weight unit as compared to that
for commonly used fuels. It may be verified that given the same
useful energy, that is at equal vehicle performance, the ratio
between storage battery weight and fuel weight is about 100, at the
actual state of the art. It is estimated that this will be lowered
to about 20 in the next years, if research projects presently under
way will provide the expected results. In other words, the useful
energy (convertible to kinetic energy) obtained, for instance, from
120 liters of diesel oil, whose weight is about 100 kilograms (this
may be assumed as a standard quantity for a motorbus), would
require today 10,000 kilograms of storage batteries and presumably
2,000 kilograms in the future.
An approach to reduce this weight, which is prohibitive for the
operation of an electrical vehicle (apart from the cost), is the
one presently on study by German manufacturers: by reducing the
range to a safe minimum (a small fraction of the one provided by
combustion vehicles) the weight and the cost of the batteries is
reduced. The batteries, however, must be replaced in a suitable
station provided with a fast loading/unloading facility and a
station network must be provided for that purpose. This solution
has the following drawbacks: the need to stop the service rather
frequently, .[.said.]. .Iadd.say .Iaddend.each hour as a minimum,
for an interval of five minutes (so the designers say), in order to
replace the batteries; the need to establish a station network in
order to replace the batteries quickly; recharging apparatus at
each station; and large capacity required for each vehicle,
considering the recharging time of a battery volume equal to that
necessary for a range of 1 day. On this subject, information may be
found in the article "German Electric Prototype Vehicle Features
Fast `Refuel` Stops" in Product Engineering, May 1971, Page 23.
Another approach, aiming to provide an ideal urban transportation
system, has been followed unsuccessfully by the Swiss firm
OERLINKON in the fifties: apparently the vehicle was a trolley-bus,
since it was provided with a trolly, but the electrical power line
was not needed. The concept followed was to produce the electric
power required for traction by conversion through a generator of
the kinetic energy stored in a flywheel, which energy in turn, was
taken by conversion, through a motor, of the electric energy
supplied through the trolley during stops at prefixed stations.
Such a vehicle has never been placed in public use by reason of
many inconveniences: the low value of the storable specific energy
and consequently limited range (about 1 kilometer for a vehicle of
weight and performances equivalent to those of a trolley-bus); a
recharging time for the flywheel which is too long; the dynamic
accumulation of energy and, therefore, storage limited in time and
the energy decreasing by reason of friction even when unused; the
complexity of the flywheel clutch and the controls for the
motor-generator-flywheel; and serious interference with the
movement and driving of the vehicle due to the gyroscopic
precession torque produced by the flywheel during changes in
vehicle direction. Recently the same idea has been reconsidered by
a well known American aerospace company which, by means of many
technological improvements aims to increase the specific energy
stored in the flywheel so as to obtain a greater range. The
proposed vehicles would operate as a common trolley-bus for a
certain portion of their way, draining energy from the electrical
line for their movement as well as for charging the flywheel. Then
they will continue for the remainder of the way using the energy
stored in the flywheel. (See Product Engineering, July 20, 1970,
pp. 80 and Apr. 12, 1971, pp. 54).
SUMMARY OF THE INVENTION
The inconveniences and disadvantages of the previous described
systems are overcome by the transportation system which constitutes
the object of the present invention. The transportation system
described herein.Iadd., .Iaddend.mainly intended for urban mass
transportation, is electrically powered, and therefore
non-polluting and noiseless. According to the invention, the
vehicles are operated by electric motors fed by storage batteries
which are recharged (recharged and not replaced) at the stops with
processes of fast recharge performed with current many times
greater than the current currently supplied during traction and,
the fast recharge current being of the order of several tens times
the nominal current of the storage batteries including as much as
of the order of 100 times the nominal current, for a particularly
short time of the order of tens of seconds and normally not
exceeding 1 minute. Recharge is obtained by means of connecting
means which connect the vehicle to a distribution electrical
network having connecting points at most of the stop stations
established. With such a system, the following cumulative
advantages are obtained: high exploitation of system resources;
range adequate to the class of service considered with a safety
margin exceeding traffic incidental events; absence of phenomena
which may disturb the vehicle in its trajectory and driving
(gyroscopic effects); complete path freedom among the stop stations
(such as for motorbuses); optimization in the utilization of
storage batteries; overall investment in storage batteries limited
to the batteries installed on each vehicle; elimination along the
whole vehicle way of the electric power line with the exception of
a very short portion at most of the stop stations, and
consequently: elimination of the problems caused by the electrical
line such as installation, isolation, maintenance; and warranty of
continued service, even in the case of an electrical power lack at
the stations, at least for a duration depending on the vehicle
range.
BRIEF DESCRIPTION OF THE DRAWINGS
These features and advantages will appear more clearly from the
following description when considered in connection with the
attached drawings in which:
FIG. 1 shows in a perspective schematic view a vehicle suitable for
the transportation system described herein and a stop station
provided with connections for fast recharge of the vehicle
batteries;
FIG. 2 shows schematically in an elevation view the electrical
connection means between a vehicle and a feeding station of FIG. 1;
and
FIG. 3 shows schematically the layout of an urban transportation
system and the stop-feeding stations according to the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
All urban mass transportation vehicles, in their intrinsic service,
follow predetermined ways, divided into stretches by a sequence of
stops or stations, suitably spaced. The distance between stops,
related to the vehicle characteristics and to the urbanization
density, is conditioned by the users' needs. Generally, it is
considered that users must walk for less than half a kilometer in
order to reach the closest stop. Therefore, as a rule, the stops
provided for urban public vehicles are in the range of a few
hundred meters, with a maximum near to one kilometer for
undergrounds and a minimum of about 200 meters for surface means
(see "1971 Urban Technology .[.conference.].
.Iadd.Conference.Iaddend." which reports 8 succession of motion
cycles, interrupted by stops, more or less short, at the stop
stations, to allow the entrance and exit of the passengers.
Authoritative international commissions for the study of urban
transportation means have determined that the average time for
running a stretch between two stops is generally less than 1 minute
and increases to 2 minutes in severe traffic. The stop time at the
stations is normally between 5 and 15 seconds. From these
observations it may be deduced that for urban vehicles of today the
stop time is, on the average, one-tenth of the effective running
time and usually becomes one-twentieth. If the motion of such
vehicles is further considered, it may be observed that the
traction work is never applied continuously along the whole
stretch, but rather there are segments which normally are run by
inertia and the always present segment corresponding to the last
portion of the stretch, before each stop, which is effected with
braking. This means that traction energy is applied generally for a
time which does not exceed 10 times the stop interval.
The present invention is founded on these considerations and
exploits the capability, recently verified in certain types of
storage batteries, to accept intermittently, without damage, and
many times. but during short intervals of application, very strong
recharging currents, for instance in the order of many tens times
the nominal discharging current. Universally known and followed
recommendations prescribe long recharging times for storage
batteries, generally in the order of many hours, with maximum
current in the order of the nominal discharging current and this is
made to avoid damage to the plates and excessive electrolyte
heating with consequent gas generation. However, it has been found
that, in certain kinds of storage batteries, such phenomena occur
in response to currents much stronger than the nominal current,
only after a certain time interval. That is, such phenomena
practically do not occur if the application of a normally high
current is contained in a limited number of seconds, which
incidentally is the duration of the stop time at the stations for
an urban vehicle. In fact, at the actual status of the art, certain
kinds of batteries, such as, for instance, nickel-cadmium batteries
can be quickly recharged by virtue of their low internal resistance
which reduces heat development and priming of the above mentioned
phenomena. Performed tests, supported by wide reports, show clearly
that such batteries can be recharged at about 90 percent of their
capacity in times of the order of 30 minutes. Also, it has been
found that the same batteries can supply very strong discharging
currents and in the regular way, without damage. Currents may be in
the order of 100 times the nominal current (nominal current is by
standard one-fifth of the value which represents the capacity in
Amp.-hours) provided such discharges are limited to short times in
the order of 1 minute. It has also been found that batteries of
this type may be charged without damage with charging currents of
the same order of magnitude (100 times nominal current) for times
in the order of some tens of seconds if suitable control procedures
for the charging voltage are followed. Such procedures are, for
instance, described in THE ELECTRO-CHEMICAL SOCIETY CONVENTION-FALL
JOINT REPORT-CLEVELAND-OHIO-- Oct. 3/7, 1971. Such capability of
fast partial recharge, alternated with discharge periods or rest
periods, provides feasibility for an electrical traction vehicle
particularly suitable for the above described urban service and
leads to the transportation system which is the object of the
present invention. For such kind of service, in fact, a battery
powered electrical vehicle may receive, during stops and by effect
of a fast recharge, the same energy amount used for running a
stretch. As will be presently described in greater detail, the
battery powered vehicles of the transportation system of the
present invention are connected rapidly and automatically to an
electric power network at each of a plurality of recharge stop
stations. The power network supplies charging current to the
batteries carried by the vehicle with a current having a magnitude
which is much greater than the nominal current of the batteries. In
particular, very strong recharging currents of the order of many
tens times the nominal discharging current are provided to the
batteries and may indeed be as large as currents of the order of
100 times the nominal current. This high recharging current is
supplied for the relatively brief period of time the vehicle is
located at a recharge stop station, which time will be of the order
of tens of seconds and in normal operation will be less than 1
minute.
For example, let us consider a vehicle having performance
equivalent to that of a normal trolley-bus. The continuous
electrical installed power for this vehicle averages 70 Kwatt.
During start, the used power is greater than normal power in the
order of 100 Kwatt. Such power is requested during the acceleration
phase for a period of about 10 seconds. The remainder of the
stretch, till the next stop, is with an average power used of 25
Kwatt, which is required to maintain the movement. This portion of
the stretch, requires an average of 25 seconds. In the terminal
phase of the stretch, it is normally considered that during braking
the kinetic energy is recovered and converted by the same
motor-generator to electrical energy. In spite of that, and in
order to make the example simpler, we will assume that no recovery
devices are provided and that the whole kinetic energy is wasted.
By this assumption the energy required to run a stretch is:
where
E.sub.s = Start Energy
E.sub.m = maintenenace energy.
Therefore: ##EQU1## Such energy may be easily provided to a storage
battery carried by the vehicle, by means of a fast recharge
operation. Assuming the voltage used by the transportation system
is 500 V. and that the available recharge time is 14 seconds, the
recharging current which must be adopted to supply again the used
energy, with a recharge efficiency of 0.7 is about 340 A. To have a
ratio between charging current and storage capacity equal to 10,
which ratio has been proved to be fully acceptable for a fast
recharge, an installed capacity of 34 Amp.-hours is required.
Related to the adopted voltage, this means a capacity of 17
Kwatt-hours. Since the capacity available from presently
manufactured alkaline nickel-cadmium batteries is at 25 Watt-hours
per each installed kilogram and 50 Watt-hours per each cubic
decimeter of volume, a storage battery of about 650 kilograms and a
volume of about 0.32 M.sup.3 is required to meet the desired
capacity. Such values are fully acceptable for a vehicle whose dead
weight is about 8000 kg.: the total weight of the batteries and the
motor, is slightly greater than the weight of a diesel engine and
related apparatus. Since the nominal current is equal to one-fifth
the battery capacity in Amp.-hours, the 34 Amp.-hours capacity in
the above example corresponds with a nominal current of 6.8 A.
Thus, in this example, the recharging current of 340 A. has a
magnitude which is 50 times the nominal current. In addition, it
has to be remarked that the above installed capacity allows the
vehicle to run at least 10 to 15 stretches without any recharge and
therefore it offers an extremely high safety margin to allow the
most complete mobility of the vehicle in the urban area even if,
for any reason, it is impossible to effect the fast recharge in one
or more subsequent recharging stations. In addition, since the stop
at the terminals are generally longer, it is eventually possible to
complete the energy recovery in such places, and it may be
concluded that it is not required that all the stop stations be
provided with recharging devices (for instance, auxiliary
stops).
The stations enabled for the fast recharge operation must not
demand any particular operation by the driver. They must be
suitably equipped so as to allow an automatic connection, quick and
reliable, of the vehicle to the recharging line, thus providing the
maximum exploitation of the stop time available. By way of example,
in FIGS. 1 and 2 is shown an arrangement which satisfies the
requirements above: 1 indicates a conductive rod, which can be made
suitably heavy and rigid in order to sustain a certain thrust by
the vehicle body 12, and suitably long so as to allow the
connection of more than one vehicle. The rod, connected to a pole
of the electrical distribution network 10, is supported by posts 2
(which at the same time may support a shelter) at a suitable
distance from the street edge and at the standard height for
trolley-lines. Under the rod, perpendicularly and for the same
length, a metallic plate 3 is embeded in the street. The plate is
connected to the other grounded pole of the distribution
network.
The unipolar contacting device 4, which may be a simple rod trolley
or a pantograph trolley, carries on the top a sufficiently long and
transversely disposed contact bar 5. When, during the braking
phase, the vehicle slips beneath the contacting rod 1, the bar 5
touches the tapered portion of the rod 1 and, sliding in contact
with it, is lowered and commands the fast descent of a sliding shoe
or contacting wheel 6 down onto the plate 3 so that the recharge
circuit closes. The command may be obtained through a switch 8
which is switched by the lowering of the trolley 4. The switch may
command a servosystem 9 (which may be electrical, hydraulic or
pneumatic) which establishes the contact between sliding shoe 6 and
plate 3. The same movements and commands are inversely performed at
the start of the vehicle so that the recharging time may be
increased in respect to the effective stop time by the addition of
two short movement intervals it is it provided that the recharging
operation occurs automatically, for the whole time in which the
electrical contact is established.
In addition, since it is possible to have a wide contacting
surface, of at least 2 cm.sup.2 no resistance problems arise, and
the current intensity may be kept within acceptable limits. A power
line, completely independent from the vehicle's path, connects the
stations. The isolation of this line, may be made in a conventional
way with better and cheaper results than that obtainable with
contacting lines from trolley-buses or trolley-cars.
Furthermore, a station may be used contemporaneously for many lines
so that a whole urban mass transportation system may be arranged
with a limited number of stations, still leaving the maximum
freedom to the lines' routes. FIG. 3 shows schematically such a
feature. The routes are represented with solid lines. Each station
is represented by a small circle. Some of them, indicated by the
letter S are provided with fast recharging devices and are
connected to a feeding line. The electrical feeding line 10 for
such devices is represented with dotted lines and is connected to a
power station 11. Clearly, the electrical feeding network may be
connected to more power stations. Looking at FIG. 3, it may be seen
that the electrical feeding network is completely independent from
the routes of the vehicles. Therefore, it may be arranged according
to minimum cost criteria, maximum efficiency or other factors which
may be completely free from the routing requirements, except for
what concerns the recharging stations. In other words it may be
said that, while conventional transportation systems are based on a
network structure, and therefore on a rigid structure, the
transportation system according to the invention is based on a
junction structure (recharging stations) which allows the same
flexibility till now provided by motor-transportation systems. It
must be further pointed out that the distribution network 10 may be
conveniently of the bipolar type, so that ground current returns
are not needed and damaging leakage currents are prevented.
The urban transportation system described above considers the
utilization of free routing vehicles, but it is clear that the
invention may be applied also to rail vehicles, such as
trolley-cars, underground vehicles, suburban railways, and, by
suitable modifications, also to transportation systems using boats
having predetermined docking points as well as to private internal
transportation systems employing electrical trucks and
elevators.
* * * * *