Land vehicles – Wheeled – Attachment
Patent
1982-09-30
1986-01-14
Mitchell, David M.
Land vehicles
Wheeled
Attachment
182 90, 182196, B60R 302
Patent
active
045642052
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to step assemblies and more particularly to flexible step assemblies that are used on heavy construction equipment that operate in very rugged terrain.
2. Background Art
Current heavy construction vehicles are often provided with step assemblies to facilitate the accessibility of the operator's station. Since vehicles of this type operate in very rough terrain, the necessary ground clearance usually requires the placement of a step below the main frame of the vehicle. While being at a convenient height for operator accessibility, the positioning usually subjects the step assembly to contact with uneven ground and/or other obstacles encountered in off-highway operation, which may result in severe damage that could render the step inoperative.
Conventional step configurations that have been developed to accommodate such physical abuse are typically shown in U.S. Pat. No. 4,054,299, which is fashioned from a length of flexible cable having a foot supporting member formed thereon that hangs in a loop from the vehicle frame. While the cable allows the step assembly to accommodate large impact forces as it is struck by various obstacles, it is usually so flexible that it is allowed to swing horizontally under the weight of an operator as he mounts the step assembly. In addition to being unstable, the swinging of the step can often cause the operator's shin to bang against the frame structure.
Other step arrangements such as those disclosed in U.S. Pat. Nos. 3,854,752 and 4,053,172 both of which are assigned to the assignee of this application, employ step assemblies that have very sturdy support brackets that are pivotally mounted to the vehicle. As an obstacle is encountered the pivoting action of the brackets and the overall bulk of the components prevents the step assembly from becoming damaged to the point of inoperativeness. In these types of step assemblies, however, the structure is quite complex and they tend to be rather costly.
Still other step designs, such as those disclosed in U.S. Pat. No. 3,967,695, which is assigned to the assignee of this application, and U.S. Pat. No. 3,603,429 disclose step assemblies that are flexible enough to withstand impact from obstacles and have some provision to resist horizontal swinging of the step under the weight of an operator. Both designs employ a deformable stiffener of resilient material such as rubber or similar elastomeric material to supply the necessary lateral rigidity to prevent the step from swinging. It is well known that the concentrated stresses inherent in this particular type of environment often result in premature failure of the resilient material.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a step assembly is disclosed that is extremely flexible so as to absorb any impact upon contact with an obstacle without damage while also being capable of becoming substantially rigid in a lateral direction when an operator places his weight upon the step as he mounts or dismounts the vehicle.
The step is suspended from the frame of the vehicle by a pair of chain assemblies. Each chain assembly is comprised of interlocking links. Each link is triangular in cross section and interacts with an angle formed by the overall shape of each link. This interaction between the similar angles allows the links to wedge together upon application of a downward force.
Thus, the chain construction of the present invention provides the necessary durability that previous "chain type" steps have exhibited in the past. Yet, the particular construction and relationship between the chain links of the present invention is such that it displays the ability to "lock-up" under the operator's weight to provide a stable platform from which he may enter and exit the operator's station. The flexible step arrangement as disclosed herein solves both problems previously set forth while retaining a very simple constru
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patent: 3967695 (1976-07-01), Waddell
patent: 4053172 (1977-10-01), McClure
patent: 4054299 (1977-10-01), Urbaitis
Hendrickson Vergil P.
Shookman Dennis R.
Caterpillar Tractor Co.
Mitchell David M.
Perry William C.
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