Apparatus for checking alignment of tandem flangeless monorail wheels

On a truck comprising tandem flangeless wheels riding on a single rail and four guide rollers rotatable on vertical axes, two at each side of the rail, crabbing and turning misalignments of the wheels are diagnosed from information about which rollers rotate during truck movement in each direction along the rail. For obtaining that information, a small reflective spot is delineated at an eccentric location on the upper surface of each roller, and a photoelectric sensor for each roller, magnetically attached to the truck, has its optical axis aimed at the orbit of the spot to issue an electrical impulse for each roller rotation. A signal device connected to each sensor issues a perceptible signal for each impulse. The signal devices are at a single console to facilitate comparisons of the number of revolutions made by the several rollers during a truck movement.

FIELD OF THE INVENTION 
This invention relates to apparatus for detecting misalignment between 
flangeless tandem wheels that ride along a single rail and are kept on the 
rail by a pair of guide rollers at each side of the rail, rotating on 
vertical axes; and the invention is more particularly concerned with test 
equipment which can be quickly installed on and removed from a truck 
comprising flangeless wheels and cooperating rollers and which provides 
information about both the nature and the degree of any misalignment of 
the flangeless wheels. 
BACKGROUND OF THE INVENTION 
Rail mounted cranes and certain other types of machines that are mounted 
for travel through limited distances along define paths have trucks that 
comprise a tandem pair of flangeless wheels that roll along a single rail. 
To confine the flangeless wheels against movement off of the rail, each 
truck also comprises guide rollers rotatable on vertical axes, two at each 
side of the rail. 
Such flangeless wheel trucks have significant advantages over trucks with 
flanged wheels. A wheel flange affords guidance to a rolling wheel by 
making sliding engagement with the rail, and it thus produces a 
substantial amount of friction that increases power requirements and 
causes wear on the wheel and the rail. A flangeless wheel truck, by 
contrast, produces only rolling friction and bearing friction, both of 
which are negligible in comparison to the sliding friction of a flanged 
wheel. Furthermore, the bearings for the flangeless wheels and for the 
guide rollers that cooperate with them need only support radial loads, 
whereas the bearings for a flanged wheel have to support substantial axial 
thrust loads as well as radial loads; hence, a flangeless wheel system can 
have less expensive bearings which nevertheless have a longer service 
life. 
To some extent the advantages of a flangeless wheel system are lost if the 
flangeless wheels are out of alignment, that is, if their axes are not 
accurately parallel and transverse to the longitudinal centerline of the 
rail. It will be apparent that if the axis of a flangeless wheel is skewed 
to a substantial extent, the wheel tends to run off of the rail but is 
confined against doing so by the guide rollers, so that the wheel rolls 
along in a constant skid that creates power consuming friction, wears the 
wheel and the rail, and imposes an axial thrust load upon the wheel 
bearings as well as imposing an abnormally high radial load on the 
bearings for at least one of the rollers. 
With these considerations in mind, it is obviously desirable to check the 
alignment of flangeless wheels, not only during the initial assembly of 
the system but also from time to time thereafter to detect and correct any 
misalignment that may have developed in service. Heretofore, however, 
there has been no simple and reliable means for accomplishing such 
checking. 
Ordinarily, the wheels and rollers of a flangeless wheel truck are 
relatively inaccessible and are therefore somewhat difficult to see. 
Rotation of the guide rollers can afford important clues to the nature and 
degree of any misalignment, but the rollers are especially hard to observe 
when the truck is moving along the rail. Even if one or two rollers are 
visible, a satisfactory determination of the nature and degree of any 
wheel misalignment requires a knowledge of what all four rollers are doing 
during a movement of the truck, and one person cannot observe rollers on 
both sides of the rail at one and the same time. 
SUMMARY OF THE INVENTION 
The general object of this invention is to provide simple, inexpensive and 
very effective apparatus for checking the alignment of flangeless wheels 
that roll on a single rail, capable of providing information about the 
nature and the degree of any misalignment of the wheels and capable of 
being quickly and easily installed on and removed from a truck embodying a 
flangeless wheel system. 
A more specific object of this invention is to provide apparatus that 
presents, at a convenient location, information which signifies the number 
of rotations made by each of the rollers of a flangeless wheel truck 
during a movement of the truck along a rail on which the wheels ride, from 
which information the nature and degree of misalignment of the flangeless 
wheels can be readily determined.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
A flangeless wheel truck 5 of the type that presents the problem addressed 
by the present invention comprises a sturdy frame 6 which carries tandem 
flangeless wheels 7 that have horizontal axes 7a and four guide rollers 8 
that rotate on vertical axes. The flangeless wheels 7 roll along a single 
rail 9, and the guide rollers 8, two at each side of the rail 9, cooperate 
with the rail to prevent the wheels 7 from riding off of it. As here 
illustrated, the truck 5 is confined against tilting from side to side by 
an upper rail 10, spaced above the rail 9 and extending parallel to it, in 
cooperation with a pair of stabilizing rollers 11, one at each side of the 
upper rail, which rotate on vertical axes. 
The weight of the truck 5 and any machine (not shown) that it supports is 
carried by the two flangeless wheels 7, which in turn impose that load 
upon the rail 9. Usually the wheels 7 are power driven for movement in 
each direction along the rail 9. The four guide rollers 8, all of which 
are freely rotatable, are arranged in pairs, the two rollers of each pair 
being laterally aligned at opposite sides of the rail and the two pairs 
being spaced apart by a substantial distance along the rail to afford good 
directional guidance to the truck. 
It is to be observed that the guide rollers 8 of each pair are spaced apart 
by a distance slightly greater than the width of the rail 9, so that if 
the rail is straight (as is normally the case) no more than two of the 
four rollers will be in contact with it at any time. This lateral spacing 
of the rollers 8 minimizes rolling friction between the rollers and the 
rail and prevents wide spots in the rail from imposing high loads upon the 
bearings for the rollers; but, more important from the standpoint of the 
present invention, it makes possible the diagnosis of any misalignment of 
the flangeless wheels 7. 
When the flangeless wheels 7 are in correct alignment--which is the 
condition illustrated in FIG. 4A--their axes 7a are accurately parallel 
and accurately transverse to the longitudinal centerline of the rail 9, 
and they are radially aligned, with one exactly behind the other. 
Accurately aligned wheels 7 tend to track straight along the rail 9; 
hence, none of the four guide rollers 8FR, 8FL, 8RR or 8RL will be 
consistently engaged with the rail while the truck is in motion. It will 
be apparent that through the course of a number of movements of the truck 
along the rail in both directions, with the wheels 7 in proper alignment, 
every roller will have made about the same number of revolutions as each 
of the others. 
FIG. 4B illustrates a condition in which the wheel axes 7a are properly 
aligned--that is, they are accurately parallel and transverse to the 
longitudinal centerline of the rail--but in which the wheels are out of 
radial alignment, in slight laterally offset relation to one another. 
Because their axes 7a are properly aligned, the wheels 7 will run 
straight, and the guide rollers 9 of a truck in the condition illustrated 
in FIG. 4B will behave in the same manner as those of a truck in the FIG. 
4A condition. 
FIG. 4C illustrates a condition of turning misalignment of the flangeless 
wheels 7, wherein the axis 7a of at least one of those wheels is oblique 
to the longitudinal centerline of the rail and wherein the wheel axes 
intersect at one side of the rail so that the truck has a tendency to 
turn. In the condition illustrated in FIG. 4C, the truck tends to turn to 
its left as it moves both forward and rearward along the rail. In this 
case, when the truck is moving forward its front right roller 8FR and its 
rear left roller 8RL will engage the rail and will rotate; whereas in 
rearward movement the other pair of diagonally opposite rollers 8RR and 
8FL will engage the rail and will rotate. 
FIG. 4D illustrates a condition of crabbing misalignment of the flangeless 
wheels 7, wherein the axes 7a of both wheels are oblique to the centerline 
of the rail, both being skewed in the same direction The front of the 
truck is again assumed to be at the left side of the drawing. With the 
illustrated crabbing wheel misalignment, the two rollers 8FR and 8RR at 
the right side of the rail will engage the rail and rotate during forward 
movement of the truck, while the two left rollers 8FL and 8RL will engage 
the rail and rotate during rearward movement. 
Thus, the nature and direction of any misalignment can be determined by 
identifying the particular two rollers that rotate during movement of the 
truck in each direction. 
For each type of misalignment the severity of misalignment can be 
determined by moving the truck alternately in one direction and the other 
and observing the distance that the truck moves along the rail from each 
point of reversal to the point where a pair of rollers begins consistent 
rotation by reason of firm engagement with the rail. 
The apparatus of this invention comprises means for detecting rotation of 
each of the guide rollers of a flangeless wheel truck and for producing a 
perceptible signal in response to each revolution of each guide roller, 
the signal being of such character that the number of revolutions made by 
each roller during a truck movement can be readily compared with the 
number of revolutions made by each of the other rollers during the same 
truck movement. From such a comparison the nature and extent of flangeless 
wheel misalignment can be diagnosed on the basis of roller behavior as 
explained above. 
For detecting roller rotation, a localized light reflecting area 14 is 
delineated on the upper surface of each guide roller 8, preferably by 
means of a small piece of a known type of reflecting adhesive tape. This 
reflecting spot 14 is of limited extent in the direction circumferentially 
of the roller and is located at a distance from the axis of the roller 8 
to move in an orbit as the roller rotates. 
Mounted above each guide roller on the truck frame 6 is a photoelectric 
sensor 16 which has its optical axis aimed at a point on the orbit of the 
light reflecting spot 14 on the roller. Desirably the sensor 16 is one 
that comprises a light source which emits light of a color distinguishable 
from ambient lighting and which responds to a reflection of that emitted 
light by emitting an electric current. A typical sensor suitable for the 
purpose is commercially available from Banner Engineering Corporation, as 
its SM 502. Each sensor 16 is preferably secured to the truck frame 6 by 
means of a magnetic clamp. 
It will be apparent that with each sensor 16 properly aimed at its roller 
8, the sensor will issue an electrical impulse output for each revolution 
of the roller, as the reflecting spot 14 passes through the optical axis 
of the sensor. As will also be apparent, two or more circumferentially 
spaced reflecting spots 14 could be applied to each roller, so that a 
corresponding number of impulse outputs would be issued by the sensor for 
each revolution; but it has been found that a single reflecting spot 14 on 
each roller provides sufficient accuracy for most purposes and has the 
advantage of simplicity. 
For each sensor 16 there is a signaling device, each signaling device being 
connected with its sensor by means of a suitable cable 18. The four 
signaling devices are mounted on a common console 19 at which they are 
readily visible. Each signaling device can comprise a light emitter 20, 
such as a small light bulb or a light emitting diode, which illuminates in 
response to each impulse output from its sensor 16. With these light 
sources 20 appropriately identified, their blinking as the truck moves 
back and forth along the rail identifies the guide rollers 8 that are 
rotating and thus enables diagnosis of the condition of alignment of the 
flangeless wheels. 
Since quantitative information about the degree of any misalignment is 
conveyed by information about the number of revolutions made by each 
roller in the course of each of a succession of back and forth traverses, 
each sensor 16 is preferably connected with a resettable counter 22 that 
records the number of electrical impulse outputs issued by the sensor 
since a resetting of the counter. The light sources 20 are not essential 
if counters 22 are incorporated in the apparatus, and counters 22 are not 
strictly necessary with light emitting signaling devices 20, but inclusion 
of the two types of signaling device is believed to give the most accurate 
results and to facilitate reading of the output signals and interpretation 
of their diagnostic significance. 
The sensors 16 and the signaling devices 20 and/or 22 normally require a 12 
to 18 v. d.c. power supply, which can be provided for by means of a small 
converter 24 which is connected with the signal device console 19 or built 
into it and which can be plugged into a 115 v. a.c. power supply system at 
a utility outlet (not shown). Thus, for checking the alignment of the 
flangeless wheels 7 of a crane, spots of reflector tape are applied to the 
rollers 8, the sensors 16 are magnetically affixed to the truck frame 6, 
and the console 19 and power supply unit 24 are taken to the crane cab, 
where the power supply is plugged into the utility outlet receptacle 
normally present in the cab. The technician then observes the signals at 
the console 19 as the crane is moved through a few traverses in each 
direction along the rail. At the conclusion of the wheel realignment 
operation, the sensors are simply pulled off of the truck and the 
apparatus can be readily carried to another job site. 
From the foregoing description taken with the accompanying drawings it will 
be apparent that this invention provides simple, inexpensive, compact and 
efficient apparatus for checking the nature and degree of misalignment of 
tandem unflanged wheel that ride on a single rail and comprise a part of a 
truck that also comprises four guide rollers, said apparatus being 
arranged to provide reliable information about the respective rollers that 
engage the rail as the truck moves in each direction along it and to 
present such information in readily perceptible form at a single 
convenient location.