Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-02-21
2002-04-16
Mai, Lanna (Department: 3619)
Land vehicles
Wheeled
Running gear
C280S042000, C280S043170, C180S024010, C180S209000
Reexamination Certificate
active
06371499
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to auxiliary axle systems for load-hauling vehicles and, more particularly, to a stowable tag axle system that includes a safety latch which positively latches the axle in the stowed position when the axle is retracted or disabled for repairs. The invention provides an improved latching system for securing the tag axle which has a compact and unitary construction which readily installs on a truck body, is easily positionally adjusted and in which the mechanism is shielded from clogging debris and corrosive materials in the case of a transit mixer application.
II. Related Art
Optionally deployable auxiliary axle systems are well known and often associated with a variety of types of load-hauling vehicles, particularly those accustomed to time-varying loading, such as dump trucks, refuse collection vehicles and transit concrete mixers. Such vehicles typically include a chassis or frame, a cab and a dedicated truck body mounted on the chassis behind the cab. Such vehicles also include a forward steering axle placed near the front of the cab and one or more sets of drive axles spaced behind the steering axle, the drive axles often being provided in a dual axle arrangement. The auxiliary axle systems furnish additional load carrying capacity by adding an axle for assisting the steering and drive axles in supporting the load and in adjusting the inter-axle distance or increasing the overall front-to-rear axle span distance for the vehicle. In this manner, not only does the tag axle system assist in balancing the load carried by, for example, a transit mixing cement truck, but generally it also enables the truck to carry a higher legal total payload than would otherwise be permitted because weight restrictions placed on vehicles traveling over highways are typically measured in terms of load per axle in combination with overall spacing between the vehicle axles.
Examples of such auxiliary axle assemblies that can be selectively engaged with the ground are shown, for example, in U.S. Pat. Nos. 5,897,123 and 5,018,755. Thus, it is known to have tag axle systems generally consisting of a rear tubular cross member carrying spaced wheel assemblies and carried by a pair of spaced tag axle arms which, in turn, are pivotally mounted to the rear portion of a truck chassis according to a generally known arrangement. Linear reciprocating operating devices, typically hydraulic cylinders, or pneumatic devices are employed to pivot the tag axle system between a raised or stowed position and a lowered or ground-engaging position.
To assure that the tag axle assembly will remain in the elevated or stowed position until it is intentionally lowered to the ground-engaging position, it is known to add some type of external latching mechanism such as that which is shown in
FIG. 1
which illustrates a fragmentary side elevational view of a transit mixer with a tag axle assembly in its raised or stowed position. The view includes a portion of a vehicle frame
12
, dual axle drive wheels
14
, a mixing drum
16
partially supported by a rear mixing drum mount support frame
18
and a tag axle assembly which includes a pair of arms
20
pivotally mounted at one of their ends to the frame to the vehicle. A tag axle
22
carrying a tag wheel
24
is mounted to the opposite end of each arm
20
. A common torque tube is shown at
26
and a shaped cam plate at
28
which cooperates with a cam follower wheel
30
. Retraction air actuators are shown at
32
with associated arms
34
. A further cam link assembly is provided which includes a pair of cam link arms, one of which is shown at
40
mounted from a pivot
42
and a pair of deployment air springs, one of which is shown at
44
which is affixed to the support frame
18
of the mixing drum using suitable means and to the cam link arms
40
.
When the retraction actuators
32
are inflated, the arms
34
pull on the pivot members
36
connected to the torque tube cross member
26
to cause the tag wheels
24
to elevate to a retracted or stowed position. Conversely, deflation of the air actuators
32
and inflation of the deployment air springs
44
produces a downward force on the cam link arm
40
which is transferred to the arm roller
30
and then through the cam plate
28
of the tag assembly thereby lowering the tag axle wheels
24
.
As previously indicated, to retain the tag axle assembly in the elevated position, there is further provided an external latching mechanism which includes a hook
50
pivotally mounted at one end to the mixing drum mount
18
and situated so that it can engage a pin
52
attached to the arm
20
of the tag axle assembly at an appropriate location. The hook is further provided with a biasing spring
53
and a pneumatic hook actuator at
54
. Inflation of the actuator
54
overcomes the biasing of the spring
53
thereby releasing the pin
52
from the grasp of the hook
50
. Otherwise, the biasing spring provides sufficient force to retain the pin
52
in the hook
50
.
While this and other similar external hook arrangements have been known to function adequately, they consist of a number of parts which must be separately positioned relative to each other and aligned with the tag axle pin and the parts are exposed to mixing drum contents, acid washes and other hazards associated with the mixing and dispensing and cleanup of transit-mixed concrete. Accordingly, the parts readily become clogged with debris inhibiting operation of the spring and the pivoting of the hook to the point where operation of the hook
50
is impaired, thereby impairing the positive latching of the stowed tag axle system. In addition, corrosion of the separately attached parts leads to frequent difficult removal and replacement.
Accordingly, there remains a need for a compact and efficient safety latch system for tag axles which is easily removed and replaced as a unit and which does not have its integral operating parts exposed to the materials and cleaning agents associated with transit concrete mixing or other materials.
Accordingly, it is a primary object of the present invention to provide a compact modular safety latch for tag axles which is easily removed and replaced as an independent unit.
It is a further object of the present invention to provide a safety latch for tag axles associated with load hauling vehicles such as transit concrete mixers which has its moving parts shielded from contact with mixed cement, mixing materials and wash materials.
Other objects and advantages associated with the present invention will become apparent to those skilled in the art upon further familiarization with the specification, drawings and claims contained in this application.
SUMMARY OF THE INVENTION
The present invention provides a compact modular safety latch assembly for retaining an associated pivoting tag axle assembly in a stowed position when not in use and when the system must be retained in an elevated position with the vehicle shut off as for the performance of maintenance on the vehicle. The system employs a cylinder-operated, spring-biased pivoting hook arrangement assembled as a modular unit on a base plate for attachment to and behind the rear mixing drum mount support metal structure of a transit mixer or the like so that only the catch portion of the hook member protrudes through a slot in the support plate of the drum support structure. The modular safety latch system may be mounted through slotted openings in the plate of the vehicle which cooperate with slotted openings in the base or support plate directed in the opposite direction so that both vertical and horizontal adjustment is provided in the system for easy mounting and final alignment adjustment of the relative location of the latch hook so that the retention pin attached to the tag axle swing frame can be captured as desired. In this manner, the moving parts of the system are all located behind the metal support plate and are less likely to encounter clogging and corrosive materials in us
Mai Lanna
McNeilus Truck and Manufacturing, Inc.
Nikolai & Mersereau , P.A.
Royal, Jr. Paul
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