Vehicle mountable electrical generating system

A vehicle-mountable electrical power generating mechanism and signal transmitter, combined to constitute a self-powered generating system mountable such as on a wheel to monitor and provide an indication of certain operating characteristics of the wheel, such as the pressure of the tire mounted thereon.

DESCRIPTION 
1. Technical Field 
A driveless electrical generator mounted on a rotatable body, such as a 
vehicle wheel, for providing power to a system which monitors and provides 
operating information such as the fluid pressure of a pneumatic tire 
mounted thereon. 
2. Background Prior Art 
There is a need for a reliable, low-cost, easily installed and maintained 
device to monitor and warn of unsafe conditions in wheels and tires of 
motor vehicles. A principal limitation of prior art devices lies in the 
lack of a reliable power source for the device since all such devices must 
actuate some form of audible or visual alarm means. The preferred alarm 
system typically involves some sort of radio transmitter mounted on each 
wheel and broadcasting a warning signal to a stationary receiver mounted 
somewhere on the vehicle. Here, electrical power must be supplied to 
operate the transmitter. 
Several of the earliest types of prior art monitoring systems are 
battery-powered, such as disclosed in U.S. Pat. Nos. 3,178,686 and 
3,588,815. The battery-operated systems, while being technically feasible, 
have not found any degree of acceptance because of various limitations. 
One of the significant limitations is that a battery is subject to aging, 
and must frequently be replaced to assure operation of the system; also, a 
battery takes up substantial installation space. Further, in such 
battery-type systems, the batteries are normally mounted in close 
proximity within the wheel, and are difficult and inconvenient to remove 
and replace. Irrespective of inconvenience of replacement, all commonly 
available batteries have an additional fundamental limitation: they freeze 
and become inoperative under severe winter driving conditions. Thus, 
proposals have been made for developing a system which is not dependent 
upon a battery for its power to operate the associated signal transmitter. 
Such systems typically employ an integral electrical generator of one form 
or another for producing a local electrical voltage to power the device, 
the necessary relative movement between stator and armature element being 
provided by rotation of the vehicle wheel on which the unit is mounted as 
the vehicle is traveling. 
Several such generating systems adopt a fixed reference mechanism of the 
type disclosed in U.S. Pat. No. 2,638,274, issued to Engler, wherein a 
hub-mounted odometer employs a pendulum weight journaled to rotate about 
an axis in a housing, the housing being affixed to a wheel, with the 
pendulum journal axis disposed in prolongation of the center of the wheel 
hub. As the wheel rotates, the housing rotates with it, the pendulum 
remaining substantially stationary in the housing. The relative motion 
between housing and pendulum is coupled to drive the odometer. One 
electrical generating system using this principle is disclosed in U.S. 
Pat. No. 4,075,603, issued to Snyder, et al. In this system, a stator 
winding of generally toroidal configuration is axially mounted to be 
rotated about the axis of the toroid as the vehicle wheel rotates. A 
multi-pole permanent magnet rotor is mounted to be freely rotatable about 
the same axis, the magnet being held substantially stationary during wheel 
rotation by means of an offset pendulum weight. A similar generator to 
that of Snyder is disclosed by Tremba in U.S. Pat. No. 4,229,728. 
Another example of a vehicle-mounted electrical power generating system is 
disclosed in U.S. Pat. No. 4,163,208 to E. J. Mertz. Mertz mounts the coil 
and the permanent magnet so that they are maintained in a predetermined 
spaced relationship on the fixed portion of the vehicle and the movable 
portion of the wheel. 
A principal limitation of the prior art systems is the fact that, at low 
vehicle speeds, the electrical generating system provides inadequate 
operating voltages to associated signaling devices. A partial solution to 
this problem would be to provide a floating rechargeable battery across 
the generator output circuit, to be charged while the wheel is rotating at 
high speed, the generator being cut out, by means known to the art, at low 
speeds, or when the vehicle is stopped. However, in such systems, low 
temperatures seriously deteriorate the power of the battery. Moreover, 
such an approach is predicated on the assumption that the vehicle will, 
over a given time interval, be driven at high speeds long enough to 
adequately charge the battery. In the case of vehicles which spend a 
considerable portion of their daily road mileage in dense urban areas in 
slow-moving traffic, such conditions may not be achieved. Therefore, there 
is a present need for a unit to provide adequate electrical power output 
at low, as well as high, vehicle speeds. 
SUMMARY OF THE INVENTION 
According to the present invention, a vehicle mountable self-powered signal 
generating and transmitting system is enclosed in a housing which is 
readily adapted to be attached to a rotating member. The system provides a 
sensing signal representing the condition of the vehicle, such as the 
condition of the tire, and transmits the signal to a receiver on the body 
of the vehicle and thence to a display in the vehicle cab. 
In a preferred embodiment of the invention, the inventive generator 
consists of a housing attached to the center of the rotatable wheel to 
rotate therewith, and which has a pendulum weight or support member 
mounted on an axis within the housing, the pendulum axis being aligned 
with the axis of the wheel so that the pendulum remains stationary while 
the wheel rotates. A gear system, cooperating with the pendulum, drives a 
pancake armature in an overspeed relation to the rotation of the housing 
to generate electrical power. 
In another embodiment of the invention, the housing itself is freely 
mountable in an offset position about the wheel axis to depend therefrom 
as a pendulum, rotational drive being supplied from a mounting shaft fixed 
along the wheel axis and rotating with the wheel. Internal gearing drives 
a pancake armature into rotation with respect to a magnetic structure 
fixed in the housing, again at a substantially higher speed than the wheel 
rotation rate. Other embodiments of the internal pendulum type drive 
similar pancake generators into overspeed rotation. 
In another embodiment, an electrical generator mounted on the pendulum is 
rotated by a drive gear engagement of the generator shaft with a drive 
gear mounted on said axis and fixedly attached to the housing. Power 
takeoff to a transmitter mounted in the housing is by conventional slip 
rings. The gear engagement is designed to drive the generator at a 
rotational speed well in excess of the wheel rotation rate. 
In one application of the embodiments of the invention, a pressure 
transducer is attached to a valve stem of a tire to monitor the pressure 
therein. When the pressure increases beyond a desired level or drops below 
a desired level, a transmitter provides a signal warning of the change to 
a receiver unit to give the operator a visual or audio indication of the 
operating condition for the particular tire. 
The same concept can be utilized to monitor various other conditions of the 
vehicle, such as its speed, the number of miles that the vehicle has been 
driven, or abnormal vibrations by using sensors of types well-known in the 
art.

DETAILED DESCRIPTION 
As will be described fully hereinbelow, the present invention comprises a 
device which is mounted on the wheel of a vehicle, such as a truck. Refer 
first to FIG. 10 of the drawings, which generally discloses a vehicle 
environment for the present invention, and more particularly a 
semi-trailer truck, generally designated by reference number 1. As is 
common, vehicle 1 has a cab 2, with two steerable wheels 4 under the cab 
and sets of dual wheels 12 supporting the tractor. 
As is well-known, the tires for these types of vehicles are very expensive; 
and, thus, it is desirable to obtain a maximum amount of mileage for any 
given tire. Also, importantly, if one or more tires of the vehicle are 
"flat", or not fully inflated, safety may be compromised. To obtain 
maximum tire mileage, to improve the operation of the vehicle from a 
safety aspect, and to reduce maintenance costs, the structural integrity 
of the tire must be maintained; and, preferably, should be monitored 
continuously. One of the most significant factors is to maintain proper 
tire pressure at all times since an undetected loss in pressure leads to 
operational problems, such as a rise in temperature and an increased 
rolling resistance, resulting in increased fuel consumption, reduced 
vehicle reduction and steering control and stability, potential loss of 
tire structural integrity, and generally reduced vehicle capabilities. 
In order to monitor tire pressure and other conditions for a vehicle, U.S. 
Pat. No. 3,930,224, issued to R. G. Whiting, entitled Transmission of 
Information (incorporated herein by reference), discloses an overall 
circuit which is capable of monitoring various conditions for numerous 
tires on the vehicle. However, as indicated therein, one of the 
difficulties that has been encountered in implementing such a system from 
a practical and operational standpoint is in mounting the transmitting 
unit in a closed and protected area on the vehicle wheels. 
Refer now to the schematic circuit of FIG. 2, useful in the present 
invention, and which shows a plurality of radio frequency receiver units 
generally labeled 6 which are operatively interconnected to a central 
display unit 8 that is preferably located in the cab of the vehicle. Each 
of the receiver units 6 is positioned adjacent the respective wheels of 
the vehicle, and is supported on the frame for receiving a signal that is 
transmitted by a wheel-mounted signal generating device, including an 
electrical energy generating device or power generator 18. According to 
the present invention, such signal generating system includes an 
electrical potential or energy generating means that is enclosed and 
sealed within a housing that is readily attached to a wheel at an exposed 
location, and incorporates a transmitter 47 that is capable of 
transmitting a signal to each of signal receiving units 6. 
Refer now to FIGS. 1 and 8, which illustrate an electrical energy 
generating unit 18, in accordance with the invention. Unit 18 includes a 
casing or housing 19 that is cylindrical in shape and having a closed end 
19A and an open end, not numbered. FIG. 8 is a view in cross-section of 
the unit 18 of FIG. 1, showing the cooperative detail of the assembled 
elements of the unit. 
A mounting stud 27 is axially affixed to the outer surface of closed end 
19A. A ring or flange 19B is formed along the periphery of the open end to 
provide a means of securing a cover 21 to the casing 19. A shaft 80 is 
axially affixed in line with mounting stud 27. The shaft includes an 
enlarged end or shoulder 80A. A circular drive gear 102 is fixedly mounted 
by its axial aperture 102A on the enlarged end 80A of shaft 80. As can be 
appreciated, the shaft 80 will rotate when the mounting stud 27 and 
housing 19 rotate. Likewise, gear 102, mounted on enlarged end 80A, also 
rotates with shaft 80 and casing 19. 
A weight is slideably mounted by bearings 88 on shaft 80 as a pendulum 86, 
and remains relatively stationary when shaft 80 is rotated. A driven gear 
104, mounted on one end of a shaft 106, extends through aperture 86C in 
pendulum weight 86. Gear 104 is engaged and driven by gear 102. Shaft 106 
is affixed at its other end to gear plate 107. Gear 107 engages and drives 
gear 108, which is mounted by bearings 100 on shaft 80. Note that other 
suitable bearings, labeled 88 and 105, are mounted on shafts 80 and 106, 
respectively, to enable proper rotating relation between parts. 
Rotation of gear 102 causes gear 104 to rotate, which in turn causes shaft 
106 and the second drive gear 107 to rotate. Rotation of gear 107, in 
turn, drives second driven gear 108 to rotate at a desired overspeed 
dependent on the selected gear ratios between gears 102 and 104, and 
between gears 107 and 108. Note that pendulum 86 and gear 108 are 
slideably mounted or journaled on shaft 80 by bearings 88 and 100, 
respectively, and do not rotate with shaft 80. More specifically, pendulum 
86 remains in a relatively stationary (that is, non-rotating) condition; 
and gear 108 rotates at a speed higher than the speed of rotation of the 
shaft, dependent on the selected diameters and gear ratios, as stated 
above. In the embodiment of FIGS. 1 and 8, gear 102 is several times 
larger in diameter than gear 104; and, hence, gear 104 rotates at a 
correspondingly higher rate of speed than gear 102, or in an "overspeed" 
relation. 
Gear 108 includes an axially extending portion 64, which is fixedly 
received in aperture 64B of hub 64A of a pancake armature 66. Thus, 
pancake armature 66 rotates with gear 108. The armature is mounted in 
close propinquity to and facing permanent magnet pole pieces 68 and within 
circumferential magnet holder 69. The pole pieces 68 are mounted along the 
inner periphery of holder 69. A plate 70 provides a magnetic return 
structure, i.e., a return flux plate, and is positioned adjacent the 
opposite side of the armature on the periphery of the holder 69. The 
pancake armature 66 is thus rotated adjacent the magnetic pole pieces 68 
at an overspeed relation to the pole pieces, as compared to the rotation 
of the casing 19. As is well-known, as the armature 66 rotates in the 
magnetic field produced by the array of magnets or pole pieces 68, an 
electrical potential is generated. Electric brush assemblies 72, mounted 
on dielectric disc 76, bear against the pancake armature to couple the 
electrical potential to a transmitting system 47, as will be described 
hereinbelow. 
The pancake armature 66 is shown in somewhat more detail in FIG. 7, and is 
of conventional multi-layer design specifically suited to those 
applications where minimal armature volume is desirable. 
It should be recognized that the diameters of gears 102 and 104 must be 
different in order that an overspeed function be obtained and that 
armature 66 is rotating faster than the shaft 80 and casing 19. Also, the 
gear ratios of gears 107 and 108 are selectable, dependent on the speed of 
rotation desired. 
As illustrated in FIGS. 3 and 3A, the casing or housing 19, which is 
preferably circular in plan view, has a substantially U-shaped bracket 26 
secured to the exterior surface thereof through stud 27 and nut 7. The 
bracket 26 has two legs that are respectively attached to the rim of a 
wheel, such as dual wheel 12, by suitable studs 28. The casing 19 of the 
electrical energy generating device 18 has a pair of flexible electrical 
conduits 11--11, respectively connecting electrical leads to pressure 
sensing switches in a sensor 20, mounted on valve stems 15 of the 
respective tires on wheels 12 and connected internally in the housing 19 
to actuate the transmitter 47 (see also FIG. 2). 
In operation, and as the vehicle is being driven along the road, electrical 
power is being constantly supplied by the inventive generating system to 
power the radio frequency transmitter 47. A suitable control signal is 
passed into the radio frequency transmitter 47, such as from a tire valve 
sensor as disclosed in U.S. Pat. No. 3,860,772 (incorporated herein by 
reference), and as indicated in FIG. 2 herein, to actuate the transmitter. 
Thus, with the vehicle in motion, the generator provides power to the 
system, including the transmitter 47, which, in conjunction with the 
sensor 20, continuously monitors a predetermined condition in a given tire 
to produce a warning signal broadcast out of antenna 49, to be picked up 
by a receiver 6 and an audio/visual display unit 8 to serve as a warning 
to the vehicle operator. The transmitter 47, the antenna 49, the receiver 
6 and the display unit 8 may all be items well-known in the art. 
Note, in FIG. 4, that the transmitter 47 and the antenna 49 may be mounted 
on the pendulum 86. However, in such arrangement, means would have to be 
provided to pass the sensor signal to the now stationary radio 
transmitter. A stationary antenna may be mounted upon the pendulum element 
86, the only restriction being that at least a substantial portion of the 
housing 19 or the cover 21 be of substantially electrically non-conducting 
material to satisfactorily enable signal emission from the housing 
assembly. 
The pressure sensors 20 contain adjustable electrical switches that open or 
close at settable threshold tire pressures, one such assembly being 
functionally designated as a switch means 3 (see FIG. 4). The pressure 
sensors 20 continuously monitor the pressure for each of the tires, and 
may be of any suitable known type, as, for example, shown in U.S. Pat. No. 
3,860,772, issued to Byrd and incorporated herein by reference. 
According to the present invention, signal generating device 18 is a 
completely enclosed, self-powered unit that can be readily attached to the 
hub or other portion of a wheel, and which is capable of powering a 
transmitter and/or a sensor for monitoring any desired condition according 
to the type of sensor employed. 
FIG. 4 is a view in cross-section of another embodiment of the invention. 
In FIG. 4, the assembly 18 includes the cup-shaped housing 19, which has 
the open end thereof covered with a cover 21, which is secured, as at 22, 
to provide a weather seal. A central support bushing 23, also 
weather-sealed as at 25, extends through a centrally positioned hole on 
the cover 21. Support bushing 23 is recessed to receive one end of a shaft 
80, which is affixed to mounting stud 27. Rotation of the associated wheel 
(FIG. 3) thus serves to rotate the housing 19, causing shaft 80 to rotate 
synchronously therewith. 
A spur drive gear 31 is fixedly mounted on shaft 80 and rotates therewith. 
An electrical generator 35, of suitable known design, is mounted on a 
pendulum weight 86, which-is freely rotatable about shaft 80 on bearing 
37. The axial position of the pendulum weight on the drive shaft is 
constrained by retainer rings or washers 41. As the housing 19 rotates, 
shaft 80 and its affixed drive gear 31 also rotate. The generator 35, 
however, being disposed at the end of pendulum 36, remains substantially 
stationary with respect to shaft rotation in position at the lower portion 
of the housing 19. The generator 35 is thus mounted in a para-axial 
relation to the axis of rotation of the wheel; that is, the axis of 
rotation of the generator is offset from or eccentric to the axis of 
rotation of the associated wheel. Generator shaft 33 is driven to rotation 
with respect to the generator 35 by engagement of a driven gear 32 
compatible with the rotating drive gear 31. The generator output is 
coupled by leads 38 to brushes 43, contacting slip rings 42 rigidly 
affixed to the hub of drive gear 31. Power takeoff may be derived from the 
slip rings 42 by a variety of means, which may involve passage through the 
hub of the gear 31, as indicated schematically by the dotted lines, to 
couple electrical power to transmitter 47 through leads 44 mounted on the 
wall of housing 19. From the relative diameters of gears 31 and 32, it 
will be seen that the generator shaft 33 is driven at a substantially 
higher rate of speed than the wheel rotation rate. 
FIG. 5 shows another embodiment of the inventive structure, wherein the 
housing 19 is stationary. In the embodiment shown in FIG. 5, the housing 
assembly is freely rotatable on sealed bearing 53 about shaft 80, which 
extends axially from the mounting stud 27. The disposition of the masses 
of the remaining components of the housing, as well as an optional 
eccentric weight 54 insures that, as the tire of the vehicle rotates to 
drive stud 27 to rotation, the housing 19 will remain in a substantially 
stationary position, with the appropriate weight 54 continuously disposed 
closest to the ground. The shaft 80, affixed to the mounting stud 27, 
carries the rotation of the mounting stud to a drive gear 56, which in 
turn drives driven gear 52 to rotate an armature shaft 60, supported at 
both ends by spindle bearings 62. Rotation of shaft 60, in turn, causes an 
affixed armature hub 64 and pancake armature 66 into rotation. The array 
of magnetic pole pieces 68 is mounted on holder 69 opposite the flux 
return plate 70. As stated above, rotation of armature 66 through the 
magnetic field induces an electrical voltage in the armature, which is 
picked off by spring-loaded brushes 72 carried by brush carriers 74 
mounted on a brush carrier plate 76. Electrical leads (not shown) conduct 
electrical power from lugs 78, connected to the brush carriers 74 and 
leading to the transmitter 47. 
In this embodiment, electrical conduits 11 enter the housing 19 through the 
mounting stud 27; and, by means of brush slip rings and leads 67, 
communicate the appropriate information from sensor 20 to transmitter 47 
for logic determination. In FIG. 5, the transmitter 47 is shown mounted in 
the upper surface of the housing 19; however, it may equally well be 
disposed on the brush carrier plate itself since the housing 19 and the 
brush carrier plate 78 are rigidly interconnected. 
FIG. 6 shows another embodiment of the generating system. Details of lead 
feed-through, and transmitter and antenna placement, have been omitted. 
FIG. 6 has certain similarities to the structure shown in FIG. 4. Here, as 
in FIG. 4, the mounting stud 27 is rigidly affixed to the housing 19 to 
drive the housing into rotation as the vehicle moves along. A shaft 80 is 
securely affixed to the stud 27, and is driven thereby. A perforated drive 
gear 82 is rigidly affixed to shaft 80, and is configured with a circular 
array of drive holes 84 around the periphery thereof. A pendulum gear 
carrier 86A of appropriate weight is freely rotatable about shaft 80 on 
bearing 88. The gear carrier 86A supports a freely rotatable vertical 
shaft 90, disposed at right angles to the shaft 80, and is held in place 
by spindle bearings 92 at both ends, the lower spindle bearing 92 being 
retained in place by two collinearly disposed set screws 94. Shaft 90 
carries a sprocket gear 96, which engages the holes 84 of the perforated 
drive gear 82. The pendulum assembly, being freely rotatable about the 
driven shaft 80, remains in a substantially perpendicular disposition at 
all times. The rotation of shaft 80 is thus transmitted to rotate the 
sprocket gear 96, which reverses rotation by engaging perforations 97 of a 
second driven perforated gear 98 mounted on armature hub 64, carrying 
pancake armature 66. The armature hub 64 is freely rotatable about shaft 
80, being carried on bearing 100. A magnetic structure 69, consisting of 
an array of magnets 68 and a return flux plate 70 rotating with housing 
19, induces a voltage in the armature 66, which is picked up by a brush 
system similar to that shown in FIG. 5. It will be noted that the armature 
66 is driven in the opposite direction from that of the housing 19, 
resulting in a relative rotation rate between them equal to twice the 
housing rotation rate. 
FIG. 9 represents another embodiment of the inventive system, having a 
narrow profile and wherein the entire structure rotates, with the 
exception of the armature assembly. This is accomplished by affixing a 
weight 110 to the armature hub 64 and armature 66, the armature hub being 
freely rotatable with respect to the shaft 80. Mounting stud 27, housing 
19, shaft 80, the brush carriers and the magnetic structure assembly are 
all carried around with the housing as the wheel rotates. Weight 110, 
through hub 64, keeps the armature 66 substantially non-rotating, the 
induced voltage being picked off by a brush assembly as in the embodiment 
of FIGS. 6 and 8. 
FIG. 11 is a cross-sectional view of still another embodiment of the 
present invention, further minimizing the narrowness of profile. FIG. 11 
includes the mounting stud 27, casing 19 and cover 21, similar to the 
embodiment of FIG. 1. The structure of FIG. 11 includes a pendulum unit 
86, similar to that shown in FIG. 1, wherein the weight of pendulum 86 is 
rotatably mounted on shaft 80 by suitable bearing assembly 88. Note, in 
this embodiment, that housing 19 rotates while the pendulum 86 remains 
relatively stationary. A pancake armature 66 is mounted on hub 64 and 
affixed to shaft 80; and, thus, the armature 66 rotates with the housing 
19. In this instance, the permanent magnets 68 are mounted on a suitable 
holder 69, with return flux plate 70, then onto the pendulum 86, and 
remain substantially stationary with the pendulum 86 when the armature 66 
rotates with the stud 27 and housing 19. The armature hub 64 contains the 
transmitter 47 and, therefore, needs no slip rings, having a direct 
connection to the armature windings. The whole wire system, pancake 
armature, transmitter, antenna and sensor switch rotate together. Note 
that, in this embodiment, the housing 19 can be made quite narrow in 
longitudinal dimension which, in many cases, provides an advantageous 
structure for mounting onto the wheel of the associated vehicle. 
The present invention discloses a wheel-mounted electrical power generator 
for a radio warning system actuated by tire pressure sensors, which is 
capable of providing a warning to the driver of the vehicle of low 
inflation in each tire sensed. The unit is self-contained and 
weatherproof, requiring external connection only to a tire pressure 
sensor, and in some designs to an external antenna. The generators 
disclosed also employ overspeed gearing systems capable of providing 
substantial output voltage at very low wheel rotation rates. 
While, for the purpose of illustration, various forms of this invention 
have been disclosed, other forms thereof may become apparent to those 
skilled in the art upon reference to this disclosure; and, therefore, this 
invention shall be limited only by the scope of the appended claims. For 
example, belts, or gear chains and sprockets, may be used in lieu of 
gears. Also, the alarm system employed need not be of the radio frequency 
transmitter variety, but may alternatively employ a wheel-mounted alarm, 
such as a flashing lamp, to convey a visible warning to the driver.