Axle vent

An apparatus for mounting a wheel on a vehicle such as a trailer includes a hollow, non-rotatable axle, a wheel hub having a cavity therein and a valve or venting structure positioned between the axle and the wheel hub cavity. The wheel hub has an end connected to the hollow axle and its other end is sealed by an end cap. The cavity within the wheel hub has a volume of air which is substantially less than the volume of air within the axle. The valve is formed by a flexible membrane or diaphragm having a slit therein. The valve opens and closes in response to pressure differentials created between the wheel hub cavity and the axle by the membrane flexing to open or close the slit.

BACKGROUND OF THE INVENTION 
This invention is generally directed to an apparatus for mounting a wheel 
on a vehicle such as a trailer or the like. More particularly, the 
invention contemplates a novel valve or venting structure which prevents 
the build-up of pressure within the wheel mounting apparatus. 
Apparatus for mounting wheels on trailers are well-known in the art. Such 
apparatuses generally include a hollow axle and wheel bearings lubricated 
by a bath of oil or light grease contained in a cavity defined by a hollow 
wheel hub. A slip ring type seal is provided between the wheel hub and the 
axle to prevent oil from leaking out at one end of the wheel hub and an 
end cap is provided at the other end of the wheel hub in order to contain 
the oil therein. 
A small hole or a sintered metal plug is provided through the end cap for 
preventing the build-up of pressure formed under heating conditions of 
operations within the wheel hub which might force oil through the slip 
ring seal. The small hole or sintered plug, however, are subject to being 
blocked with grease or oil so as to become inoperative. 
The present invention presents a novel valve or venting structure for an 
axle which is used to mount a wheel on a vehicle such as a trailer that is 
intended to overcome this problem and other inherent problems in the prior 
art as well as to present several other advantages and improvements. 
OBJECTS AND SUMMARY OF THE INVENTION 
A general object of the present invention is to provide a novel venting 
structure which substantially prevents the build-up of pressure within a 
vehicle wheel mounting apparatus due to heating conditions which occur 
during operation of the vehicle. 
An object of the present invention is to provide a venting structure for a 
wheel mounting apparatus venting system having a novel structure that 
effectively minimizes the possibility of the venting structure becoming 
inoperable. 
Briefly, and in accordance with the foregoing, the present invention 
discloses an apparatus for mounting a wheel on a vehicle such as a 
trailer. The apparatus generally includes a hollow, non-rotatable axle and 
wheel bearings lubricated by a bath of oil or light grease contained in a 
cavity defined by a hollow wheel hub. A slip ring type seal is provided 
between the wheel hub and the axle to prevent oil from leaking out at one 
end of the wheel hub. A closed end cap is provided at the other end of the 
wheel hub in order to contain the oil therein. The volume of the cavity in 
the wheel hub is substantially less than the volume within the hollow 
axle. 
A valve is positioned between the hollow axle and the wheel hub cavity and 
is formed from a flexible membrane having a slit therein. The slit in the 
valve membrane opens and closes in response to pressure differentials 
created between the volume of air in the wheel hub cavity and the volume 
of air which is within the axle in order to prevent the build-up of 
pressure due to heating conditions of operations within the wheel hub 
cavity which might force oil through the slip ring seal. The valve opens 
and closes by the membrane flexing to open or close the slit. 
The valve may further include a generally rigid member which encircles the 
flexible membrane and which generally conforms to the shape of the 
interior of the hollow axle. A flexible seal, such as a flexible flap, may 
be provided along the outer surface of the member for sealing the member 
to the interior of the axle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
While the invention may be susceptible to embodiment in different forms, 
there is shown in the drawings, and herein will be described in detail, a 
specific embodiment with the understanding that the present disclosure is 
to be considered an exemplification of the principles of the invention, 
and is not intended to limit the invention to that as illustrated and 
described herein. 
In FIG. 1, and as used in accordance with the present invention, an 
apparatus 20 for mounting a wheel (not shown) on a vehicle, such as a 
trailer or the like, is shown. The apparatus generally includes an axle 
22, a wheel hub assembly 24 and a brake assembly 26. 
The axle 24 is fixedly mounted on the trailer body by suitable means and is 
formed from a hollow tube 28 having ends (only one of which is shown) 
having a hollow spindle 30 attached thereto by, for example, a weld 32. 
The spindle 30 is a hollow, tapered member having a threaded end 34. The 
hollow tube 28 and spindle 30 of the axle 22 define a volume therein. The 
axle 22 is formed from a suitable strong rigid material. 
The brake assembly 26 is of known construction and as such is not described 
in detail herein. The brake assembly 26 is mounted on the axle 22 and 
generally includes a brake drum 36 and a brake shoe 38. 
The wheel hub assembly 24 is mounted on the end of the axle 22 and 
generally surrounds the spindle 30. The wheel hub assembly 24 includes a 
wheel hub 40 having a space, chamber or cavity 42 therein, a plurality of 
wheel bearings 44 and an end cap 46. The wheel hub 40 is attached to the 
brake drum 36 by suitable known means, such as bolts 48. 
A bath of oil or light grease 50 is contained within the wheel hub cavity 
42. The oil or light grease 50 lubricates the wheel bearings 44 and the 
axle 22 during operation of the vehicle. The cavity 42 in the wheel hub 40 
defines a volume which is substantially less than the volume within the 
hollow axle 22. 
A slip ring type seal 52 is provided between the wheel hub 40 and the axle 
22 to prevent the oil or light grease 50 from leaking out from the cavity 
42 at the intersection of the wheel hub 40 and the axle 22. The end cap 46 
is a one-piece uninterrupted member, except for apertures through which 
the end cap 46 is attached to the end of the wheel hub 40 by suitable 
means, such as bolts 54. The end cap 46 seals the outer end of the hub 
cavity 42 and prevents the oil or light grease 50 from leaking out of the 
end of the wheel hub assembly 24. 
The wheel bearings 44 are mounted between the wheel hub 40 and the spindle 
30 by an inner bearing cup 56 and an inner bearing cone 58. An inner 
adjusting nut 60 is threaded onto the threaded end 34 of the spindle 30 
and bears against the inner bearing cone 58 and a shoulder 62 formed in 
the spindle 30 to position the wheel bearings 44. The adjusting nut 60 is 
locked onto the spindle 30 by threading a lockwasher 64 and an outer jam 
nut 66 on the threaded end 34. 
The wheel bearings 44 allow the wheel hub assembly 24 and the brake drum 36 
to rotate relative to the fixed axle 22. The bearings 44 are mounted on 
both sides of the cavity 42 and are lubricated by the bath of oil or light 
grease 50 contained within the cavity 42. 
During operation of the vehicle, as the wheel, wheel hub 40, end cap 46 and 
brake drum 36 turn, heat is generated. This causes the air within the 
wheel hub cavity 42 to expand and thus the pressure to increase. Also 
during operation, some oil or grease 50 may leak into the end cap 46 
through the space between the inner bearing cup 56 and cone 58 where the 
wheel bearings 44 are located. 
In order to prevent the build-up of pressure created under heating 
conditions of operations within the wheel mounting apparatus 20, a novel 
valve or venting structure 68, as shown clearly in FIGS. 2 and 3, is 
provided. The valve 68 is positioned within the axle 22 and may be 
positioned within the spindle 30. The valve or venting structure 68 is 
located between the volume of air within the hollow axle 22 and the wheel 
hub cavity 42. The valve or venting structure 68 opens and closes in 
response to pressure differentials created between the volume of air 
within the axle 22 and the volume of air within the cavity 42 during 
operation of the vehicle. 
The valve 68 is a soft, flexible membrane or diaphragm 70 that is made of a 
suitable material such as a soft flexible polymer, for example, neoprene, 
urethane, latex or the like. A small, narrow slit 72 is provided within 
the diaphragm 70 to provide for opening and closing the valve 68 in 
response to pressure differentials created during operation of the 
vehicle. The slit 72 is defined by abutting edges 74, 76 of the membrane 
70. 
When the valve or venting structure 68 is closed, the abutting edges 74, 76 
of the membrane 70 lie in an abutting position as shown by the solid line 
in FIG. 2. When the valve or venting structure 68 is open, the edges 74a, 
76a of the slit 72 are apart, as shown in phantom lines in FIG. 2 which 
are exaggerated for illustrative purposes only. To open the valve 68, the 
membrane 70 flexes either concavely or convexly thus parting the edges 74, 
76. The slit 72 is capable of passing or venting air, but the slit 72 is 
sufficiently narrow so as to preclude any appreciable passage of oil or 
grease 50 which may have accumulated in the end cap 46. The slit 72 also 
prevents the passage of any rust or other foreign material that may have 
accumulated inside the axle 22 into the wheel hub assembly 24 where the 
rust or foreign material might foul the bearings 44. 
If oil, grease or dirt accumulates on the valve 68, the slit 72 in the 
resilient diaphragm 70 effectively minimizes the possibility of the valve 
68 becoming plugged or inoperable. If there is any build-up in pressure 
because of an initially plugged slit 72, the diaphragm 70 flexes to a 
greater degree to open the slit 72 wider. 
The valve 68 may further include a generally rigid member 78 encircling the 
flexible membrane or diaphragm 70. The member 78 is made of a suitable 
material, such as a relatively rigid plastic. The exterior shape of the 
member 78 generally conforms to the interior shape of the hollow axle 22. 
A flexible sealing member 80 may be provided along the outer surface of the 
rigid member 78 to provide for a tight seal or fit between the member 78 
and the interior of the axle 22 to minimize or prevent any dirt, rust or 
oil from passing around the perimeter of the valve 68. The sealing member 
80 may be a flexible flap along the outer perimeter of the member 78 as 
shown in FIGS. 2 and 3. Alternatively, the sealing member 80 may be a 
bead, such as an annular bead, which encircles the member 78 along its 
outer perimeter. 
Now that the specifics of the novel valve 68 and associated wheel mounting 
apparatus 20 have been described in detail, the operation of the valve 68 
will be described. As the wheel, wheel hub assembly 24 and brake drum 36 
turn relative to the axle 22, heat is generated. This causes the air 
within the wheel hub cavity 42 to expand and thus the pressure to 
increase. Since the volume of air within the axle 22 is relatively cool, a 
pressure differential is created. 
The valve 68 opens in response to the pressure differential by flexing 
inwardly toward the axle 22 and causing the slit 72 to open, as shown in 
exaggerated form by the phantom lines in FIG. 2. Air from the wheel hub 
cavity 42 passes or vents into the axle 22 until the pressure between the 
cavity 42 and the volume of air within the axle 22 has been equalized. 
Once equalization is achieved, the valve 68 closes by the edges 74, 76 of 
the slit 72 in the membrane 70 abutting each other as shown by the solid 
line in FIG. 2. Thus, the axle 22 provides an effective space into which 
the excess air pressure in the wheel hub assembly 24 can be vented and 
this prevents the build-up of any appreciable pressure in the wheel hub 
cavity 24 since the volume of air within the axle 22 is many times that of 
the cavity 24. The axle 22 acts as a heat sink and dissipates the heat 
into the atmosphere. When the operation of the trailer is stopped and the 
wheel hub assembly 24 is allowed to cool, the air pressure in the wheel 
hub assembly 24 may decrease to a level below that of the air in the axle 
22. In this event, the valve diaphragm 68 will flex outwardly to open the 
slit 72 and permit the air pressure within the wheel hub cavity 42 and the 
axle 22 to equalize. 
While a preferred embodiment of the present invention is shown and 
described, it is envisioned that those skilled in the art may devise 
various modifications of the present invention without departing from the 
spirit and scope of the appended claims. The invention is not intended to 
be limited by the foregoing disclosure.