Hub lubrication system

A hub-axle assembly (10) and lubrication system thereof includes a spindle (11) having an inner end (12) and outer end (15) with inner (13) and outer (14) bearing assemblies spaced axially on the spindle (11). A hub body (16) is rotatably supported on the bearing assemblies (13, 14) and has a wheel mounting flange (17) extending radially outward therefrom. Lug bolts (18) extend axially outward from the flange (17) with one such lug bolt (18) having an axial bore (24) therein. Grease applied at a grease fitting (23) in the axial bore (24) is transmitted to a lubrication chamber (19) within the hub body (16) via tubing (25) to lubricate the lubrication chamber (19). A circumferential recess (27) in the hub body (16) has at least one aperture (28) therein which is normally closed by an O-ring (29) positioned in the recess (27). However, when the pressure of the grease within the hub body (16) is sufficient to indicate that the lubrication chamber (19) has been lubricated, the O-ring (29) will expand causing grease to flow through the aperture (28).

TECHNICAL FIELD 
This invention relates to a system for lubricating axle-hub assemblies of 
vehicles. More particularly, this invention relates to such a system 
wherein complete greasing of the axle-hub assembly can be efficiently, 
conveniently and economically accomplished. 
BACKGROUND ART 
Conventional axle-hub assemblies include a stationary axle or spindle which 
supports spaced front and rear bearings which, in turn, support a 
rotatable hub. When greasing these axle-hub assemblies, and particularly 
those which may be submersed in water as, for example, in the situation of 
a hub assembly for a boat trailer, it is important that grease is applied 
to both the front and rear bearings and to otherwise effect a complete 
lubrication of the axle-hub assemblies. 
To date, no system has been economically developed which conveniently and 
efficiently assures the user that the entire axle-hub assembly has been 
greased. One existing system requires that an axial bore be drilled 
substantially along the entire length of the spindle. Grease is applied 
into the axial bore through an opening in the end cap, travels through the 
entire axial bore and exits the same through radial bores in the spindle 
at a location behind the inner bearings. The grease then travels back 
through the inner bearings, between the hub and the spindle, through the 
outer bearings, and into the open end cap where it can be observed by the 
user indicating a complete greasing. 
Such a system has been found to be deficient in many regards. First, the 
manufacture thereof is quite expensive requiring the time-consuming 
drilling of the axial bore and a special end cap having an aperture 
therein and means to seal the same. Further, application of the grease 
takes longer inasmuch as it must first travel from the end cap through the 
entire length of the spindle and then back to the end cap. In addition, 
with the grease entry and exit points being at the same general location, 
the messy discharge of grease onto the users hands cannot usually be 
avoided. 
Another existing system is shown in U.S. Pat. No. 4,172,620. There, grease 
is introduced through the hub behind the wheel support portion thereof. 
The grease then passes through the inner bearing, then between the spindle 
and the hub, then through the outer bearings, and then out through a 
special opening in the end cap to provide an indication of complete 
greasing of the assembly. Such a system is inconvenient for the user in 
that he must reach blindly behind the wheel support portion of the hub to 
locate the grease fitting. Further, a special end cap is required to 
permit grease to pass therethrough, which passage also exposes the user to 
the grease. 
DISCLOSURE OF THE INVENTION 
It is thus a primary object of the present invention to provide a 
convenient, economical and efficient system for completely lubricating a 
hub assembly. 
It is another object of the present invention to provide a system, as 
above, in which the grease application point is conveniently accessible to 
the user and yet the grease is admitted to the hub behind the inner 
bearings. 
It is a further object of the present invention to provide a system, as 
above, which gives a visual indication of complete greasing of the 
bearings of the hub at a location in front of the outer bearings without 
undue discharge of grease. 
These and other objects of the present invention, which will become 
apparent from the description to follow, are accomplished by the 
improvements hereinafter described and claimed. 
In general, a hub assembly includes a spindle having an inner end 
attachable to an axle and an outer free end. Inner and outer sets of 
bearings are spaced along the spindle and rotatably carry a hub body which 
encases the spindle. A wheel mounting flange extends radially outwardly 
from the hub body with lug bolts extending axially outwardly from the 
flange. The system for lubricating the hub assembly includes means to 
introduce grease within the hub body at a location on one side of one of 
the sets of bearings, as by a grease fitting mounted in one of the lug 
bolts, along with means to transfer the grease to the hub body. The system 
also includes means to permit the controlled discharge of the grease from 
the hub body to indicate a greasing of the hub assembly, as by providing a 
circumferential recess in the hub body at a location on the outer side of 
the one set of bearings, the recess having an opening therein, and as by 
providing means to close the opening while permitting the controlled 
discharge of grease therethrough.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION 
A hub assembly including the lubrication system of the present invention is 
indicated generally by the numeral 10 in FIG. 1. While hub assembly 10 is 
of the type which can be used for the stationary axle of any vehicle, hub 
assembly 10 is most typically used for towed vehicles such as trailers or 
the like. 
Hub assembly 10 includes a spindle indicated generally by the numeral 11 
which is attachable in a conventional manner at its inner end 12 to the 
stationary axle of the vehicle. Hub assembly 10 also includes a 
conventional inner bearing assembly 13 adjacent inner end 12 of spindle 11 
and an outer bearing assembly 14 spaced from bearing assembly 13 and 
generally adjacent the outer end 15 of spindle 11. Bearing assemblies 13 
and 14 rotatably support a hub body 16 in a conventional manner. A wheel 
mounting flange 17 extends radially outward from hub body 16 and is 
provided with a plurality of lug bolts 18 for attachment to a wheel in a 
conventional manner. Hub body 16 of hub assembly 10 thus forms, with 
spindle 11, a lubrication chamber 19 closed on the inner end by 
conventional seals 20 and at the outer end by an enclosure in the form of 
cap 21. A spindle nut 22 holds the hub body 16 in place on spindle 11. 
It is important, particularly in situations where the hub assembly may be 
submersed in water, that lubrication chamber 19, and in particular inner 
bearing assembly 13 and outer bearing assembly 14, be maintained 
lubricated with grease. To that end, a conventional grease fitting 23 is 
pressed into one of the lug bolts 18 so that it is conveniently accessible 
to the user. A bore 24 is drilled through the lug bolt 18 associated with 
fitting 23 and tubing 25 is attached to the inner end of bolt 18 thus 
communicating with bore 24. Tubing 25 is designed to convey grease applied 
at fitting 23 to lubrication chamber 19 and, as such, as shown in FIG. 1, 
tubing 25 extends through hub body 16, as at 26, preferably at a location 
inwardly of inner bearing assembly 13, that is, between bearing assembly 
13 and seals 20. 
Grease applied at fitting 23 travels through bore 24 of lug bolt 18, 
through tubing 25 and into chamber 19. Continued pressurized application 
of grease causes it to flow through and lubricate inner bearings 13, 
continue moving through chamber 19 in the direction of the arrows in FIG. 
1, and be forced through outer bearings 14 thereby lubricating the same 
and completely lubricating the system. 
In order to provide a visual indication of such complete lubrication, hub 
body 16 is provided with a circumferential recess 27 preferably located on 
the outer side of outer bearing assembly 14, that is, between bearings 14 
and end cap enclosure 21. Recess 27 communicates with lubrication chamber 
19 by means of at least one radial bore 28 therein. Radial bore 28 is 
closed by an O-ring 29 positioned in recess 27. O-ring 29 is, however, of 
such elasticity and is thus expandable so as to permit grease to seep 
through radial bore 28 and thus appear around O-ring 29 when a certain 
predetermined pressure, such as ten p.s.i., has been exceeded within 
chamber 19. O-ring 29 therefore, while sealing bore 28, provides for the 
controlled discharge of grease giving the operator a visual indication 
that complete lubrication has taken place. 
As previously indicated, any number of bores 28 may be provided depending 
on the particular application involved. However, it has been found 
convenient to provide at least one of the bores 28, as is shown in FIG. 1, 
at the circumferential point in recess 27 which is generally coincident 
with the circumferential point of the lug bolt 18 having the grease 
fitting 23 therein so that the operator can readily and quickly determine 
that complete greasing has taken place. 
In the embodiment shown in FIG. 1 and in certain applications, grease may 
well appear around O-ring 29 before the end cap enclosure 21 is filled 
with grease. While this is normally not detrimental because the indication 
of grease indicates the complete lubrication of both bearing assemblies 13 
and 14, an air pocket could be formed in enclosure cap 21 and could 
expand, due to the buildup of heat during the operation of the vehicle, 
and cause a bit more grease to be emitted through bores 28. If it is 
desirable to avoid this unsightly occurrence, an enclosure, indicated 
generally by the numeral 30 and shown in FIG. 2, may be provided. 
Enclosure 30 is designed to be used with a hub assembly 10 as shown in FIG. 
1 and described herein. In the FIG. 2 embodiment, however, enclosure 30 
includes an annular sidewall 31, a radially directed spring bearing 
shoulder 32 near the outer end of sidewall 31, and an axially directed 
annular flange 33. The space between sidewall 31 and flange 33 serves to 
confine a coil spring 34 which bears on one side on shoulder 32 and which 
inwardly biases a piston member generally indicated by the numeral 35. 
Piston 35 includes a number of stepped surfaces including surface 36 
bearing against spring 34 and adjacent annular surface 37 bearing against 
and slidable along the inner surface of flange 33. Second stepped surfaces 
of piston 35 include a radially directed surface 38 and an axially 
directed surface 39 which together radially and axially confine a sealing 
O-ring 40. O-ring 40 is additionally axially confined by an annular lip 41 
extending axially from a piston cap 42 of enclosure 30 which in its normal 
position rests against the axially outer edge of flange 33. Lip 41 of cap 
42 is press fit and attached, as by glue, to surface 39 of piston 35 so 
that cap 42 and piston 35 will move together. 
In the FIG. 2 embodiment, as grease under pressure passes through outer 
bearing assembly 14 and begins to build up pressure on O-ring 29, it will, 
of course, also pass into the area of enclosure 30 and begin to exert 
pressure on piston 35. Based on the size of piston 35 and with proper 
selection of the spring 34, as could be determined by one of ordinary 
skill in the art, piston 35 will be essentially completely displaced 
moving cap 42 away from the outer edge of flange 33 before the grease 
displaces O-ring 29 sufficiently to appear within recess 27. As piston 35 
and cap 42 move to the left in FIG. 2, O-ring 40 slides along the radially 
inner surface of flange 33 and thereby provides a seal so that no grease 
can pass thereby. At this point the operator may discontinue applying 
grease under pressure at fitting 23 and by manually pushing cap 42 
inwardly, that is, returning piston 35 to the position shown in FIG. 2, 
further grease may be discharged through bores 28 and more potential air 
pockets in chamber 19 eliminated. While smaller air pockets may still be 
present in chamber 19, by utilizing the enclosure configuration shown in 
FIG. 2, when expansion occurs due to heat up during operation of the 
vehicle, piston 35 will be displaced to account for such expansion and no 
unsightly grease will be discharged through bores 28. 
As has been previously described, the hub lubrication system of the present 
invention is particularly suited for hub-axle assemblies which might be 
submersed in water where complete greasing is important, such as those 
assemblies used on boat trailers. It should be appreciated, however, that 
the present invention has applications to other situations where air 
pockets are not as severe a problem. For example, without departing from 
the spirit of this invention, the cap 42 and piston 35 shown in FIG. 2 
could be provided with an axial bore and a grease fitting inserted therein 
to supply grease on one side of outer bearings 14. In this instance the 
circumferential recess 27 would be located in hub body 16 on the other 
side of outer bearings 14 and grease would be discharged through bores 28 
to indicate that lubrication chamber 19 was completely greased. 
It should thus be evident that a hub lubrication system constructed 
according to the concept of the present invention, as described herein, 
substantially improves the art and otherwise accomplishes the objects of 
the present invention.