Wheel assembly

A wheel assembly especially suitable for use on large heavy refuse carts. The wheel assembly includes an axle which has been heat treated and plated to provide a central core, an outer skin on the central core of substantially increased strength and hardness, and a chromium plating on the outer skin, and the associated hub of the wheel has been heat treated to provide an annular interior skin in journalling association with the axle having an increased hardness and strength as compared to the main body of the hub. The chrome plating on the axle has a hardness in excess of the hardness of the interior hardened skin of the wheel hub. The wheel assembly is mounted between spaced parallel mounting plates on the associated refuse cart with the ends of the axle passing through apertures in the lower ends of the mounting plates and with the assembly held in place between the mounting plates by a bolt carrying a washer and threadably engaging a blind bore in one end of the axle so as to position an end plate on the other end of the axle against the outboard face of the outboard mounting plate. A pair of seals are provided at each end of the hub of the wheel and an annular grease groove is provided in the hub inboard of each pair of seals.

BACKGROUND OF THE INVENTION 
This invention relates to wheel assemblies and more particularly to wheel 
assemblies especially adapted for use with large carts such as refuse 
carts. 
With the ever increasing industrialization of our society, the need for a 
quick and efficient means of removing waste for ultimate disposal has 
steadily increased. The industry that has grown up to service this need 
has largely evolved in two directions. For relatively lighter and/or lower 
bulk waste disposal requirements, containers are provided at the user 
facility which, when filled with waste matter, are emptied into a refuse 
truck by a suitable hoisting mechanism and then replaced in position at 
the user facility to receive more refuse. In situations requiring larger 
volumes or heavier weights of refuse, the so-called "roll off" container 
or cart has been used. The roll off carts typically provide a capacity of 
between 12 and 40 cubic yards; may be used in association with an end 
compactor at the user facility; and are typically picked up and carried 
away when full on a custom vehicle, in piggyback style, with the vehicle 
carrying away the filled cart also delivering a new, empty cart to the 
user facility prior to pickup of the filled cart. These large refuse 
carts, in the course of loading and unloading onto the associated custom 
vehicle, receive considerable abuse. Since they must be dragged 
considerable distances both during the placement and the removal 
operations, they are typically provided with wheel assemblies at the four 
corners of the cart. The wheel assemblies sustain heavy abuse, not only 
because of the extremely heavy loads being carried in the carts, but also 
by virtue of the rough handling and the rough terrain over which the carts 
are dragged. The wheel assemblies in the past have generally comprised 
relatively standard designs in which a simple wheel is journalled on a hot 
rolled mild steel axle extending between parallel mounting plates on the 
corners of the cart. Due to the relatively unsophisticated design of the 
wheel assemblies and the extremely heavy abuse that the wheel assemblies 
receive, the wheel assemblies have become extremely high maintenance 
items. It is not unusual, for example, for the wheel assemblies to wear 
out to a point of being unusable in as short a time as three months. 
Typically the wheel assemblies are rebuilt, placed back in service, and 
then again rebuilt after which they again quickly wear out. A typical 
average total life of a wheel assembly, including several rebuilds, is 
about two years whereafter the entire wheel assembly must be replaced. In 
addition to the considerable expense associated with with rebuilding and 
ultimately replacing the wheel assemblies, the wheel assemblies may become 
dislodged during road transport on the associated vehicle and run wild and 
at high speed along the roadway, creating a potential for serious damage 
to other vehicles and/or personal injury. Further, since these containers 
are typically used in conjunction with an on site compactor, the cart can 
no longer be set at the proper height required for latching onto the 
compactor after it has lost a wheel assembly. Further, a container with a 
lost or severely damaged wheel assembly inflicts severe damage to the 
associated asphalt pavement onto which it is placed or over which it is 
dragged during the loading or unloading operation. Further, when a cart is 
taken out of service because of a damaged wheel assembly the cart must be 
brought into the main depot for maintenance and repair, resulting in time 
loss by the driver of the associated vehicle and revenue loss because the 
cart is out of service. 
Various attempts have been made to introduce more sophistication into the 
wheel assemblies of these refuse carts in order to reduce the maintenance 
problem. For example, various attempts have been made to incorporate 
grease fittings so that lubrication can be added to the hub and axle 
assembly; other attempts have involved the use of roller or ball-type 
bearings in the wheel assemblies; and other attempts have involved the use 
of plastic or bronze bushings in the wheel assemblies. However, none of 
these attempts to improve the durability of the wheel assemblies has met 
with any degree of commercial success. Specifically, in the case of the 
lubricated wheel assemblies, the truck drivers are often remiss in 
greasing the axles on a regular schedule, the grease fittings become 
damaged and cannot be replenished with grease, or the grease fittings 
accumulate sand and dirt making it difficult or impossible to snap on the 
grease gun fitting or, even if greasing is possible, the greasing 
operation pumps in sand and dirt which in turn causes high abrasion 
failure of the axle and hub. In the case of the roller or ball-type 
bearing designs, it has been found that the extremely high gross vehicle 
weights and extremely high shock load forces encountered by these refuse 
carts causes immediate or eventual catastrophic failure to the internal 
bearing parts. In the case of the plastic or bronze bushing designs, the 
extremely high gross vehicle weights cause material flow-type deformation 
with resultant immediate or eventual failure of the wheel assembly. 
SUMMARY OF THE INVENTION 
This invention is directed to the provision of an improved wheel assembly 
especially suitable for use with refuse carts. 
More particularly, this invention is directed to the provision of a wheel 
assembly for use with refuse carts which will provide many times the 
useful life of the wheel assemblies presently employed on the refuse 
carts. 
The wheel assembly according to the invention includes a pair of flange 
plates adapted to be rigidly secured to a respective corner of the refuse 
cart and extend downwardly from the main body of the cart in parallel 
spaced relation; and aperture in the lower end of each flange plate; an 
axle passing slidably through the apertures in the flange plates and 
presenting a journal portion of round cross section between the plates; 
and a wheel comprising a tubular hub positioned between the flange plates 
and journalled on the axle journal portion, a rim, and means 
interconnecting the rim and hub in concentric relation. This simple 
arrangement provides an inexpensive but highly durable wheel assembly 
construction that is especially suitable for handling the high gross 
vehicle loads of the associated refuse carts. 
According to a further feature of the invention, the axle journal portion 
and the hub, at their annular interface, are formed of different 
materials. This arrangement improves the wear qualities of the assembly. 
According to a further feature of the invention, the axle journal portion, 
in cross section, comprises a metallic central portion and an annular 
outer layer forming a plating on the central portion having a hardness 
greater than that of the central portion. This hard plating further 
improves the wearability of the wheel assembly. 
According to a further feature of the invention, the outer layer comprises 
a chromium layer. The use of a chromium layer further improves the 
wearability of the wheel assembly. 
According to a further feature of the invention, the central portion of the 
axle journal portion is heat treated prior to application of the chromium 
layer to form a relatively soft core and a relatively harder outer skin 
directly beneath the chromium layer. This hard skin beneath the chromium 
layer provides structural strength for the chromium layer to preclude 
"punch through" damage to the chromium layer. 
According to a further feature of the invention, the annular layer of the 
axle immediately underlying the hard outer skin has an average hardness 
substantially exceeding the hardness of the core of the axle but less than 
the hardness of the outer skin. This relatively hard intermediate layer 
provides support to the hard outer skin and coacts with the outer skin to 
provide exceptional structural integrity for the axle. 
According to a further feature of the invention, the central core of the 
axle has a hardness greatly exceeding the hardness of a typical carbon 
steel so as to further add to the structural integrity of the axle. 
According to a further feature of the invention, the hub is formed of a 
carbon steel and is heat treated to form a relatively soft annular main 
body portion and a relatively hard annular skin on the annular interior 
periphery of the main body portion. The relatively hard annular skin on 
the interior periphery of the hub portion coacts with the chromium plating 
on the axle to further enhance the wearability of the wheel assembly. 
According to a further feature of the invention, the annular interior skin 
of the hub has a hardness less than that of the chromium layer on the 
axle. This specific relative hardness at the interface of the axle and hub 
further improves the wearability of the wheel assembly. 
According to a further aspect of the invention, the axle journalling the 
hub has a length exceeding that of the hub so as to project axially beyond 
the hub at each end of the hub to provide mounting end portions for 
passage through aligned apertures in the spaced mounting plates on the 
associated body structure of the refuse container to mount the wheel 
assembly on the associated body structure and rollably support the body 
structure; a threaded bore is provided in one end of the axle; a bolt is 
provided which is sized to be threaded into the threaded bore; a washer is 
provided having an inner diameter sized to pass the bolt and an outer 
diameter greater than the diameter of the axle; and a plate member is 
rigidly secured to the other end of the axle and includes a portion 
extending radially outwardly beyond the axle. 
This wheel assembly construction allows the wheel assembly to be mounted on 
the associated body structure by positioning the hub between the body 
structure mounting plates, passing the one end of the axle through the 
aperture in one mounting plate, through the hub, and through the aperture 
in the other mounting plate to bring the plate member into engagement with 
the outboard face of the one mounting plate, and threading the bolt with 
the washer thereon into the threaded bore in the axle to bring the washer 
into engagement with the outboard face of the outher mounting plate. 
Removal of the wheel assembly for repair or replacement is similarly 
readily accomplished.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The refuse cart 10 as seen schematically in FIG. 1 includes a body 
structure 12 of generally boxlike configuration with a closed top 12a, and 
an opening or door 12b in the rear end wall 12c of the cart. A wheel 
assembly 14 is provided at each corner of the cart to rollably support the 
cart. As previously indicated, the refuse cart 10 is intended to be 
carried in piggyback fashion on an associated vehicle to the user site, 
unloaded from the vehicle, placed in a user position in association with 
an end compactor with opening 12b juxtaposed to the compactor, and 
thereafter loaded back onto the associated vehicle after it has been 
filled with refuse. 
Each wheel assembly 14 includes a pair of flange or mounting plates 16, an 
axle assembly 18, and a wheel assembly 20. 
Plates 16 are formed of a suitable steel and are welded in spaced relation 
to the underside of the body structure 12 of the cart with two plates 
provided at each corner of the cart. Each plate tapers inwardly and 
downwardly and includes a circular aperture 16a in the lower end of the 
plate. 
Axle assembly 18 includes an axle 22, an end plate 24, a washer 26, and a 
bolt 28. 
Axle 22 is manufactured from a carbon steel stock containing, for example, 
0.23% carbon, 0.80% magnesium, 0.23% silicon, 0.50% nickel, 0.50% chrome, 
and 0.20% molybdenum. The axle is machined to print specification and a 
blind threaded bore 22a is provided in one end of the axle. After 
machining, the axle is subjected to a temperature of 1,650 degress F. in 
an atmosphere of endothermic hydrocarbon generator gas for a period of 
four hours, then allowed to cool to 1,425 degrees F. The axle is then 
quenched in 70 degree F. oil. After removing the axle from the quench oil, 
it is subjected to a 350 degree F. bake for a period of two hours. This 
heat treatment process creates an axle having, in cross section and as 
best seen in FIGS. 7 and 8, a relatively soft central core 22a, a 
transient layer 22b of gradually increasing hardness, and an extremely 
hard annular outer skin 22c. As compared to a starting tensile strength of 
approximately 95,000 psi (12 R.sub.c), the heat treated axle may have an 
internal core strength of 175,000 psi (38 R.sub.c) which gradiently 
increases in layer 22b to 325,000 psi (60 R.sub.c) at the inner periphery 
of the skin 22c and maintains at 60 R.sub.c throughout the thickness the 
skin 22c. For an axle having a diameter of 1.25 inches, layer 22b may have 
a thickness of approximately 0.06 inches and skin 22c may have a thickness 
of approximately 0.04 inches. The axle is then surface ground on the 
outside diameter to an exact size within 0.0005 inches on the diameter and 
is thereafter electroplated with chromium to a thickness of 0.0005 or a 
total of 0.0010 on the diameter. The chromium layer or plating is seen at 
22d in FIGS. 7 and 8. Chromium layer 22d provides an R.sub.c of 
approximately 63. The axle is then subjected to a 350 degree F. bake to 
remove surface hydrogen generated by the electroplating process and 
absorbed by the axle surface. This relieves surface embrittlement. The 
choromium surface is then polished to a 16 microinch finish to give all 
parts a smooth running surface. 
In the completed axle 22, the chromium layer 22d provides wearability at 
the axle/hub; the skin 22c provides structural strength for the chromium 
layer to preclude "punch through" damage to the chromium layer; the 
gradient layer 22b provides support for skin 22c and coacts with skin 22c 
to provide exceptional structural integrity for the axle; and the hardened 
central core 22a provides support for gradient layer 22b and coacts with 
the other layers to further add to the structural integrity of the axle. 
End plate 24 is then welded onto the end of the axle remote from the 
threaded bore 22a to complete the axle assembly. Axle 22 has a length such 
that, when fitted in apertures 16a in mounting plates 16 with end plate 24 
positioned against the outboard face of the outboard mounting plate 16, 
the annular end face of the axle around bore 22a is substantially flush 
with the outboard face of the inboard mounting flange 16. 
Wheel 20 includes a central hub 30, a pair of wheel disks 32, and rim 34. 
The wheels at the rear of the cart are significantly wider than the wheels 
at the front of the cart to accommodate the differing loads encountered at 
the front and rear of the cart. 
Wheel hub 30 is tubular and has a central bore 30a sized to slidably pass 
axle 22 with a journal fit; has a length such that it fits loosely between 
the inboard faces of the mounting plate 16; and is preferably manufactured 
from a carbon steel containing 0.25% carbon and 0.75% maganese. The hub is 
machined to print specifications, adding seal end pockets 30b formed as 
counterbores on each end of the hub, lubrication grooves 30c formed as 
further counterbores between each seal pocket 30b and central bore 30a, 
and lubrication reservoir grooves 30d spaced inboard from each counterbore 
30b. After machining, the hub is preheated in an air furnace to 750 
degrees F. and is then transferred into a specially formulated salt bath 
containing 50% potassium cyanide and 50% potassium cyanate, at 1,060 
degrees F. The hub remains in the bath for two hours. The hub is then 
removed from the bath, allowed to cool to 700 degrees F. and quenched in 
oil, after which time it is removed and cleaned. This processing provides 
a hub which, as best seen in FIGS. 7 and 8, includes an annular core 30e 
which essentially retains its untreated tensile strength of 80,000 psi (5 
R.sub.c), and a hard nongalling interior peripheral skin 30f having a 
tensile strength of 285,000 psi (55 R.sub.c). For a hub having a nominal 
outer diameter of 2.0 inches, skin 30f may have a thickness of 0.0005 
inches. Skin 30f comprises a carbon bearing epsilon iron nitride 
containing no brittle Fe.sub.2 N. The heat treated hub is then passed 
through central apertures in the disks 32, the disks are welded to the 
hub, and the rim 34 is welded to the outer periphery of the disk 32 to 
form the wheel. Disks 32 are preferably inset with respect to the rim 34 
so that the rim overlaps the disk at each side face of the wheel. 
Prior to installing the wheel assemblies on the refuse cart, a grease seal 
36 and a wiper or contaminate excluder seal 38 are fitted into each seal 
counterbore 30b. Grease seal 36 may comprise, for example, a seal 
available from the Grover Piston Ring Division of Fluorocarbon Corporation 
of Milwaukee, Wisconsin as U-Cup Style No. 15, and seal 38 may comprise, 
for example, a seal available from the same source as U-Pack Style No.30. 
As best seen in FIG. 5, the seals are maintained in position in 
counterbore 30b by a seal retainer 40 bearing against a seal retaining 
split ring 42 received in a groove 30g adjacent the outboard end of each 
counterbore 30. 
Following positioning of the seals 36, 38 in the counterbores 30b, 
lubricant is provided in lubrication grooves 30c and 30d; bore 30a and 
axle 22 are heavily lubricated; wheel 20 is positioned between plates 16; 
and the threaded bore end of axle 22 is passed through the aperture 16a in 
the outboard mounting plate 16 and through the central bore 30a of hub 30 
for passage through the aperture 16a of the inboard mounting plate 16. As 
previously indicated, axle 30 is sized so that the threaded end of the 
axle reaches a position flush with the outboard face of the inboard 
mounting plate 16 at such time as end plate 24 moves into engagement with 
the outboard face of the outboard mounting plate 16. Washer 26 and a lock 
washer 44 are now placed over bolt 28 and bolt 28 is threaded into 
threaded bore 22a to complete the assembly of the wheel assembly to the 
refuse cart. As best seen in FIG. 6, axle 22 is precluded from rotating 
relative to mounting plates 16 by engagement of a flat side face 24a of 
end plate 24 with a confronting side face 42a presented by a key 42 welded 
to the outboard face of the outboard mounting flange 16. 
Removal of the wheel assembly for repair or replacement is readily 
accomplished by simply removing bolt 28 and sliding the axle assembly to 
the left as viewed in FIG. 3 to withdraw the axle from the mounting plates 
and allow the wheel 20 to be removed from between the mounting plates. 
The invention wheel assembly, in actual test, as compared to well 
established data with respect to the standard hot rolled mild steel wheel 
assemblies long in use in association with refuse carts, has increased 
axle strength by an estimated factor of 3.5 and has increased wearability 
of the wheel assemblies many times. More specifically, whereas the prior 
art wheel assemblies typically require rebuilding every three months and 
have been totally useless after an average life of two years, the 
invention wheel assemblies have required no maintenance during a two-year 
period of test usage and, following disassembly after the two-year period 
of test usage, have shown no significant wear. 
Whereas a preferred embodiment of the invention has been illustrated and 
described in detail it will be apparent that various changes may be made 
in the disclosed embodiment without departing from the scope or spirit of 
the invention. For example, at least in certain applications, plating 22d, 
rather than being formed of chromium, may comprise a nickel layer that is 
deposited on the axle and then baked to an R.sub.c of approximately 63.