Heretofore, military equipment such as tanks, armored personnel carriers and the like have generally comprised tracked vehicles. The advantages that are derived from the use of tracked vehicles in areas of highly adverse terrain are well known. It is also generally known that, at least for long term operation, tracked vehicles are limited to slow speeds such as 3 or 4 m.p.h. Thus, although some tanks can be driven as fast as 40 m.p.h., such operation requires the replacement of the tracks after as little as one or two days of high speed use.
The use of tracked vehicles came into vogue during World Wars I and II which were fought over vast areas and under such differing adverse terrains as beaches, farmlands, trenches, mountains, etc. Modern warfare often poses quite different problems. For example, terrorist activities or insurrections may require the deployment of military equipment over a substantial distance at very high speeds. Such deployment must be carried out under conditions of substantial comfort if the personnel involved are to arrive at the scene of conflict in a relatively fresh condition. Once at the scene the deploying vehicle must be capable of operating over highly adverse terrain including such obstacles as barricades, rubble from burned or bombed out buildings, bomb craters and the like.
Thus, a need exists for military equipment which is adapted for long term operation at relatively high speeds and under conditions of maximum comfort, while at the same time being capable of successfully negotiating various types of extremely adverse terrain. From the standpoint of practicality such equipment should resemble prior designs as closely as possible and in fact should incorporate parts common to currently utilized equipment insofar as is possible.
The present invention fulfills the foregoing and other objectives to provide an entirely unique undercarriage adapted for use with various types of military and civilian equipment. In accordance with the broader aspects of the invention, a superstructure, which may be identical to the of prior equipment designs, is supported on and transported over the underlying surface by a pair of undercarriages each incorporating the present invention. Each of the undercarriages comprises an elongate hollow primary load bearing frame. A plurality of primary axles are rotatably supported at longitudinally spaced points along the primary frame. A primary transmission mechanism extends through the primary frame for drivingly interconnecting the primary axles, and a drive mechanism is mounted on the primary frame for cooperation with the primary transmission mechanism to rotate the primary axles.
A plurality of secondary frames are pivotally supported on the primary frame, and a secondary axle is rotatably supported on each secondary frame. A secondary transmission mechanism extends through each secondary frame to provide a driving connection between one of the primary axles and the secondary axle carried by the secondary frame. Each secondary axle supports and drives a wheel member comprising an elastomeric tire. The secondary frames extend angularly downwardly and rearwardly from the primary frame and are substantially parallel to each other. Spring mechanisms urge the secondary frames to pivot away from the primary frame.
In a first embodiment of the invention, pivotal movement of the endmost secondary frames is under the action of one spring mechanism, while the pivotal movement of each center secondary frame is under the action of two spring mechanisms. By this means the wheel members of the center secondary frames engage the underlying surface under substantially greater force than the endmost wheel members, thereby facilitating skid steering of the vehicle. In a second embodiment of the invention, pivotal movement of each secondary frame is controlled by a spring/shock absorber assembly. The spring/shock absorber assemblies of the center wheels include hydraulic cylinders for normally positioning the center wheels below the endmost wheels to facilitate skid steering, and for selectively raising the center wheels for high speed operation. In a third embodiment of the invention, the pivotal movement of each secondary frame is controlled by a spring/shock absorber/hydraulic cylinder assembly. All of the hydraulic cylinders are double acting, thereby providing maximum control over the operation of vehicles incorporating the invention.
In accordance with more specific aspects of the invention, each secondary frame is hollow and contains the secondary transmission means individual thereto. Each secondary transmission means comprises a sprocket mounted on the associated primary axle, a sprocket mounted on the secondary axle rotatably supported on the secondary frame, and a drive chain drivingly interconnecting the two sprockets. Each secondary frame may include a disc brake for selective actuation to arrest rotation of the secondary axle rotatably supported therein and the wheel member carried by the secondary axle.