Auxiliary axle assembly

A liftable auxiliary axle assembly for a wheeled vehicle including an auxiliary support frame assembly connected to the vehicle frame; a pair of spaced apart torque arms pivoted on the auxiliary frame assembly about a common pivot axis so that the rear end of each is pivotally movable in a generally vertical plane; a pair of axle seat assemblies mounted on the rear ends of the torque arms for pivoting movement therewith and mounting a wheel and axle assembly therebetween; and a positioning mechanism for selectively lifting the wheel and axle assembly from the road.

BACKGROUND OF THE INVENTION 
Because it is frequently desirable to increase the load carrying capacity 
of a vehicle without increasing the maximum permissable load on each wheel 
and tire assembly of the vehicle as regulated by state law, auxiliary axle 
assemblies have been provided. A number of different auxiliary axle 
assemblies are presently available for the mounting on such vehicles. 
Usually, these auxiliary axle assemblies have the capability of being 
lifted from the road when the maximum permissable load for each wheel and 
tire assembly already provided on the vehicle is not exceeded. These 
liftable auxiliary axles are usually provided on various kinds of trucks 
where such trucks travel for a significant portion of the time during 
their use in an unloaded condition. One type of liftable auxiliary axle 
assembly is illustrated in U.S. Pat. Nos. 3,133,745; 3,325,181; 3,689,102; 
3,713,663; and 3,747,948. A different type of liftable auxiliary axle 
assembly is illustrated in U.S. Pat. No. 3,502,348. Both of these types of 
liftable auxiliary axle assemblies suffer from common problems. One of 
these problems is that it is a relatively complex and time consuming 
matter to adjust the alignment of the auxiliary axle with respect to the 
vehicle. Another common problem with these auxiliary axle assemblies is 
that the springing of the auxiliary axle and also the lifting of the axle 
is provided by air bag type springs which are subject to failure and also 
relatively expensive to replace. Another problem associated with such 
prior art axle assemblies is that the amount the axle can be lifted from 
the roadway is limited by the vehicle frame. 
SUMMARY OF THE INVENTION 
These and other problems and disadvantages associated with the prior art 
liftable auxiliary axle assemblies are overcome by the invention disclosed 
herein by providing a liftable auxiliary axle assembly which is easily 
adjustable for alignment between the auxiliary axle and the vehicle, which 
is capable of being mounted on different width vehicle frames without 
fishplating the frame to connect the auxiliary axle to the frame, where 
the auxiliary axle lift is not limited by the vehicle frame and where the 
auxiliary axle is lifted without the use of the air bag springs. 
The apparatus of the invention includes generally an auxiliary axle 
assembly with an auxiliary support frame connectable to the vehicle frame 
and which is adjustable to accept different vehicle frame widths. A pair 
of spaced apart torque arm assemblies are pivotally mounted on the 
auxiliary support frame about a common pivot axis generally normal to the 
vehicle axis so that the torque arm assembly moves in a generally vertical 
plane. The projecting ends of the torque arm assemblies each carry a seat 
assembly which mounts the auxiliary axle and the air bag spring with the 
other end of the air bag spring connected to the auxiliary support frame 
to spring the torque arm and seat assembly. The seat assemblies are 
axially movable along each of the torque arms and postitively connected to 
the torque arm so that alignment of the auxiliary axle is simplified. A 
lifting mechanism is provided for lifting the extending ends of the torque 
arm as well as the auxiliary axle independently of the air bag springs. 
The auxiliary axle can be located rearwardly of the vehicle frame so that 
the vehicle frame does not limit the amount the auxiliary axle can be 
lifted from the roadway. 
These and other features and advantages of the invention disclosed herein 
will become more apparent upon consideration of the following 
specification and accompanying drawings wherein like characters of 
reference designate corresponding parts throughout the several views and 
in which:

These figures and the following detailed description disclose specific 
embodiments of the invention, however, it is to be understood that the 
inventive concepts are not limited thereto since they can be incorporated 
in other forms. 
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
Referring to the figures, it will be seen that the auxiliary axle assembly 
10 is adapted to be mounted on a wheeled vehicle, here shown as a truck T. 
The truck T has a main frame F including a pair of spaced apart 
longitudinally extending frame side members SM which mount the main truck 
drive axle units DA thereon so that the truck T is movable along its 
longitudinal axis A.sub.T. The main frame F has a rear end RE where the 
side members SM terminate. The auxiliary axle assembly 10 may be mounted 
forwardly or rearwardly of the drive axle units DA. For sake of simplicity 
the auxiliary axle 10 is only illustrated mounted rearwardly of the drive 
axle units DA. 
The auxiliary axle assembly 10 comprises generally an auxiliary support 
frame assembly 11 mounted on the side members SM of the main frame F as 
seen in FIGS. 2-4. The auxiliary frame assembly 11 pivotally mounts a pair 
of torque arm assemblies 12 thereon which project rearwardly under the 
side members SM. The torque arm assemblies 12 mount a wheel and axle 
assembly 14 therebetween behind the rear end RE of the truck frame F. 
Positioning means 15 is provided for selectively lifting the torque arm 
assemblies 12 and wheel and axle assembly 14 from contact with the road, 
and for springing the wheel and axle assembly 14 when it is in contact 
with the road. 
The auxiliary support frame assembly 11 includes a pair of frame rail 
supports 20, one being mounted on the outside of each side member SM of 
the main frame F as best seen in FIGS. 2, 4 and 5. Each frame rail support 
20 includes a side plate 21 with an L-shaped cross-section that extends 
along the outside and under the side member SM. The forward end of the 
side plate 21 is connected to a support beam 22 which extends downwardly 
therefrom under the side member SM. The lower end of the beam 22 is 
provided with a pivot bolt 24 as will become more apparent on which one of 
the torque arm assemblies 12 is pivoted. 
The torque arm assemblies 12 as seen in FIGS. 2 and 3 have the same 
construction and only one will be described in detail. Each torque arm 
assembly 12 comprises a tubular torque arm 25 and an axle seat assembly 
35. The torque arm 25 as seen in FIGS. 2, 3, 6 and 7 has an elongate 
cylindrical bearing section 26 with a cross tube 28 at its forward end as 
seen in FIG. 6. The cross tube 28 mounts a bushing 29 therein. The bushing 
29 is rotatably mounted on the pivot bolt 24 carried by frame assembly 11 
so that the torque arm 25 is rotatable about a common torque arm pivot 
axis A.sub.TA passing through the centerline of both bolts 24. The 
rearwardly projecting end 27 of the bearing section 26 is provided with a 
threaded alignment adjustment stud 30 coaxial with the bearing section 26. 
The stud 30 has a length L.sub.1 projecting from the rear end 27 of torque 
arm 25 and a diameter smaller than the diameter of the bearing section 26 
on the torque arm 25 so that the stud 30 can be inserted into the arm 25 
and extend along substantially the entire length thereof. The stud 30 is 
usually welded to arm 25 at the rear end thereof. 
One of the axle seat assemblies 35 is mounted on each of the torque arms 25 
which serves to connect the wheel and axle assembly 14 to the torque arms. 
Each axle seat assembly 35 includes a mounting tube 36 which is slidably 
and rotatably receivable over the bearing section 26 of the torque arm 25 
so that the support tube 36 is concentric about the torque arm centerline 
CL.sub.TA. The length L.sub.2 of the support tube 36 as seen in FIG. 2 is 
less than the length L.sub.3 of the support section 26 of torque arm 25 as 
will become more apparent. An upstanding axle seat 38 is fixedly mounted 
on the support tube 36 adjacent its rear end and extends upwardly 
therefrom. The upper end of the axle seat 38 is provided wth an upwardly 
opening axle receiving recess 39 which mounts the axle tube 40 of the 
wheel and axle assembly 14. The axle tube 40 is usually welded to the axle 
seat 38. Additionally, a pair of U-bolts 41 may be used to lock the axle 
tube 40 onto seat 38 in conjunction with the tie plates 42 on opposite 
sides of the axle seat 38. It will thus be seen that the torque arm 25 can 
be rotated relative to the axle seat assembly 35 for adjustment as will 
become more apparent. 
A connector 45 is mounted on the rear end of the axle seat assembly 35 for 
use in positively locating the axle seat assembly longitudinally along the 
torque arm 25. The connector 25 defines a cutout 46 therein with an 
opening 48 thereto and a semicircular closed end 49 opposite opening 48. 
The closed end 49 is centered on the central axis of tube 36 and torque 
arm centerline CL.sub.TA with the width W.sub.1 of cutout 46 greater than 
the diameter d.sub.1 of the stud 30 and less than the outside diameter 
d.sub.2 of tube 36. 
An internally threaded adjustment member 50 is threadedly received on stud 
30 to engage connector 45 and position the axle seat assembly 35. The 
member 50 is cylindrical with an outside diameter greater than the width 
W.sub.1 of cutout 46 but less than the inside diameter d.sub.2 of tube 36. 
An annular, outwardly opening channel 51 is defined around member 50 
intermediate its end with channel 51 lying in a plane transverse of the 
central axis of member 50. The forward section 52 of member 50 is 
rotatably received in the rear end of tube 36 with the connector 45 
fitting into the channel 51 while the rear section 54 projects rearwardly 
from tube 36 and connector 45. Thus, it will be seen that the channel 51 
captivates the connector 45 therein and thus the axle seat assembly 35 
against fore and aft movement with respect to member 50. The projecting 
rear section 54 can be manually engaged to screw member 50 along the stud 
30 to positively position the axle seat assembly 35 longitudinally of the 
torque arm 25. However, it will be noted that the axle seat assembly 35 
can still rotate about the torque arm 25. The rear section 54 may be 
provided with wrenching surfaces to facilitate this adjustment. A lock nut 
55 is provided to lock the member 50 in any desired position on stud 30. 
The wheel and axle assembly 14 is conventional with the axle tube 40 
extending between the axle seat assemblies 35 and attached thereto. The 
axle tube 40 projects outwardly past opposite sides of the truck frame 
side members SM and rotatably mount hub assemblies 56 at opposite ends 
which rotatably mount rims 58 and tires 59. Air brake units AB are 
provided to apply the brakes in the hub assemblies 56. 
A lower spring seat 60 is mounted on the mounting tube 36 of each of the 
axle seat assemblies 35 forwardly of the axle seat 38 so that the 
centerline CL.sub.AS of the spring seat 60 is normal to the axle tube 40 
carried in axle seat 38. The spring seat 60 is maintained in a fixed 
relationship with axle seat 38 when torque arm 25 is rotated in the axle 
seat assembly 35. An upper spring seat 61 is mounted on the lower edge of 
each side plate 21 so that it is generally vertically aligned with the 
lower spring seat 60. The positioning means 15 includes a conventional air 
bag spring 62 attached between each vertically aligned pair of seats 60 
and 61 to spring the torque arms 25 and thus the wheel and axle assembly 
14. 
Each axle seat assembly 35 is also resiliently connected to its associated 
side plate 21 through an alignment spring assembly 65 that allows the 
spacing between the side plates 21 to be adjusted over a limited range. 
Each alignment spring assembly 65 includes an alignment spring 66 
connected to the mounting tube 36 of the axle seat assembly 35 forwardly 
of the lower spring seat 60 by an attachment tab 68. The upper end of the 
spring 66 is connected to side plate 21 through hanger 69 and hanger bolt 
70. Because the mounting tube 36 rotatably mounts the axle seat assembly 
35 on the torque arm 25 for rotation about the torque arm centerline 
CL.sub.TA and because the axle tube 40 fixes the seat assemblies 35 with 
respect to each other, the spacing between the side plates 21 prior to 
mounting on a truck can be changed by turning bolts 70 to change the 
rotational force the springs 66 exert on the side plates 21 thus causing 
the side plates 21 and torque arms 25 to rotate about the torque arm 
centerline CL.sub.TA to move the side plates 21 toward or away from each 
other. Thus, the side plate spacing can be changed to accommodate 
different spacings between the truck frame side members SM. 
A forwardly projecting alignment tube 75 is provided centrally of axle tube 
40 to be used to limit the amount of side-to-side movement of the wheel 
and axle assembly 14 as the truck turns. Such movement is commonly known 
as axle walkout. A walkout guide unit 76 seen in FIGS. 3 and 4 is mounted 
between the side members SM of the truck frame to control the walkout of 
the wheel and axle assembly 14 through the alignment tube 75. The walkout 
guide unit 76 includes a cross member 78 which is mounted between the rear 
ends RE of the side members SM. A U-shaped guide 79 depends from cross 
member 78 and defines a vertically oriented guide slot 80 therein through 
which the alignment tube 75 projects. The guide slot 80 is sufficiently 
wide that the alignment tube 75 can project therethrough while clearing 
the sides of the slot, but sufficiently narrow for the alignment tube 75 
to strike the sides of slot 80 and limit the walkout of wheel and axle 
assembly 14. 
The front end of the alignment tube 75 projecting forwardly of guide unit 
76 is provided with a lift plate 81 to be used to lift the wheel and axle 
assembly 14 and the torque arm assemblies 12 so that the tires 59 of the 
auxiliary axle assembly 10 clear the road. The positioning means 15 also 
includes a lift unit 90 mounted between the frame side members SM to lift 
the wheel and axle assembly 14. 
The lift unit 90 is best seen in FIGS. 3-5, 9 and 10 and comprises a 
support frame 91 which is carried between the side members SM and which 
mount the chain lift unit 90 centrally of the vehicle frame F. A pair of 
base tubes 92 are mounted in a spaced apart position on the support frame 
91 so that the centerline of the base tubes 92 extend generally parallel 
to the axis A.sub.T of the vehicle. A pair of extension tubes 94 are 
slidably mounted in the base tubes 92 so that the extension tubes 94 can 
be selectively extended from and retracted into the base tubes 92 along 
paths generally parallel to the axis A.sub.T. The forwardly projecting 
ends of the extension tubes 94 are provided with a cross plate 95 which 
connects them together so that both of the extension tubes 94 move in 
unison into and out of the base tube 92. The rear end of the base tubes 92 
opposite the ends of the base tubes 92 from which the extension tubes 94 
project are each provided with chain pulleys 96. Each of the chain pulleys 
96 are rotatably mounted about generally horizontal rotational axes 
A.sub.p normal to the centerline of the vehicle. A flexible lift member, 
here shown as chain 98 extends along the length of each of the extension 
tubes 94 and the base tubes 92 to project out of the rear end of the base 
tubes 92 over the chain pulleys 96. The front end of each of the lift 
chains 98 is attached to the cross plate 95 connecting the extension tubes 
94 so that the lift chains 98 will be drawn into the base tubes 92 as the 
extension tubes 94 are extended and allowed to extend from the base tubes 
92 over the chain pulleys 96 as the extension tubes 94 are retracted into 
the base tubes 92. It will be noted that the lift chains 98 move along 
spaced apart paths generally parallel to the axis A.sub.T of the vehicle 
and lie in a horizontal plane within the tubes 92 and 94. The chains pass 
from the horizontal position to the vertical position around the chain 
pulleys 96 and depend below the chain pulleys 96 where the depending ends 
of the lift chains 98 are attached to the lift plate 81 on the alignment 
tube 75 on the wheel and axle assembly 14. Thus, it will be seen that as 
the extension tubes 94 are extended from the base tubes 92, the lift 
chains 98 will lift the wheel and axle assembly 14 along with the torque 
arm assemblies 12 so that the tires 59 on the wheel and axle assembly 14 
will be lifted from the road as seen in FIG. 2 or lowered onto the road 
when the extension tubes 94 are retracted as seen in FIG. 3. A pair of 
lift cylinders 99 are also mounted on the support frame 91 between the 
base tubes 92 so that their selectively extendable piston rods 100 project 
forwardly from the lift cylinders 99 and are connected at their projecting 
ends to the cross plate 95. Thus, it will be seen that as the piston rods 
100 are extended from the lift cylinders 99, the extension tubes 94 will 
be extended out of the base tubes 92 to cause the lift chains 98 to lift 
the wheel and axle assembly 14. As the piston rods 100 are retracted, the 
extension tubes 94 are moved into the base tubes 92 to allow the lift 
chains 98 to lower the wheel and axle assembly 14 into contact with the 
road. An appropriate control is provided to charge the air bag springs 62 
when the tires 59 on the wheel and axle assembly 14 are in contact with 
the road to provide the necessary spring connection between the vehicle 
frame F and the auxiliary wheel and axle assembly 14. While two lift 
cylinders 99 are illustrated, it is to be understood that these lift 
cylinders may be replaced by a single lift cylinder. 
It will be noted that because the torque arm assemblies 12 are sufficiently 
long, the axle tube 40 of the wheel and axle assembly 14 rides behind the 
rear end RE of the vehicle frame F. This allows the lift chains 98 to lift 
the axle tube 40 of the wheel and axle assembly 14 above the lower edge of 
the side members SM to provide additional clearance above the road. 
Normally, the lift provided by auxiliary wheel and axle assemblies is 
about 8 inches above the road surface whereas this wheel and axle assembly 
is able to lift the wheel and axle assembly 14 above the road surface to 
give a clearance of about 12 inches. 
When the auxiliary axle assembly 10 is to be mounted on truck frame F, the 
hanger bolts 70 of the alignment spring assembly 65 are adjusted until the 
spacing between the side plates 21 on the auxiliary support frame 11 is 
such that the side members SM of the truck frame F will just fit between 
the side plates 21. The side plates 21 are then positioned on the side 
members SM and the holes for the attachment bolts B drilled in side 
members SM. The bolts B seen in FIG. 2 are installed to attach the side 
plates 21 to side members SM and thus mount the auxiliary axle assembly 
10. 
The lock nuts 55 are then loosened and the adjustment members 50 screwed on 
the studs 30 until the wheel and axle assembly 14 is properly aligned with 
the truck axis A.sub.T. The lock nuts 55 are then retightened to lock 
members 50 in place. 
The walkout guide unit 76 is then installed between the rear ends RE of the 
truck frame side members SM. The chain lift unit 90 is also installed 
between side members SM so that the chain pulleys 96 are generally 
vertically oriented over the lift plate 81. The lift chains 98 are 
connected to the lift plate 81. The cylinders 99 are connected to the air 
supply on the truck as well as the air brake units AB and the air bag 
springs 62. The unit is now ready for use.