Traversing hoists – Boom or mast – Extensible by sliding sections
Reexamination Certificate
1999-10-13
2001-06-12
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Boom or mast
Extensible by sliding sections
C212S231000
Reexamination Certificate
active
06244450
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of Invention
The present invention relates generally to methods of constructing and controlling moving telescoping boom sections of an aerial lift or other device and a telescoping boom constructed in accord with the method, and more particularly to a new and improved method of constructing and controlling moving telescoping boom sections of an aerial lift or other device, each of the boom sections being extended or retracted by a hydraulic cylinder and a new and improved telescoping boom apparatus constructed in accord with said method, having, for each moving section, a rigidly affixed hydraulic cylinder.
B. Description of Related Art
Many types of aerial lifts, cranes and similar telescoping boom devices have been provided. Further, many of these use a hydraulic actuator to extend or retract the boom. However, it is not believed that any of these devices use an individual hydraulic actuator for each moving section, such lifts instead conventionally using chains, cables, or the like in pulley systems to achieve the extension and retraction of the boom sections. Nor do conventional lifts have rigidly mounted hydraulic actuators or sliding supports on the hydraulic actuator piston rods.
SUMMARY OF THE INVENTION
In the present invention, an aerial lift or crane or similar device is mounted on a vehicle that may be a self-propelled chassis, a highway truck or a trailer having rearward and forward ends. A rotatable pedestal is provided on the vehicle and has an elongated telescoping boom assembly pivotally mounted to the pedestal about a horizontal axis. The outer end of the boom structure may have an aerial lift platform or a sheave for the load line or other devices for supporting the load or ancillary equipment. The present invention comprises the method of construction and control of the telescoping boom assembly comprising a main boom section fixed to the pedestal and at least two and up to four elongated moveable beam structures, all of which beams have a similar cross-sectional shape, preferably square or rectangular. The base beam and the moveable beams are elongated and hollow with successively smaller cross-sectional dimensions such that they can telescope within one another, the largest being the base beam. The moving sections of the boom are telescoped into and out of each other and the base beam by means of double acting linear hydraulic actuators connected between each moving section and the next beam section into which it telescopes. A series of switches and electric valves control the sequence of extension of the hydraulic actuators. In a five section boom, two of the hydraulic actuators are positioned within the interior of the boom sections and the other two hydraulic actuators are externally positioned. To improve the buckling strength of the hydraulic actuators, the piston rods and hydraulic cylinder cases are rigidly mounted to the stationary and moving boom sections. In order to support the long hydraulic actuator piston rods that are externally positioned along the elongated boom, sliding supports are provided. The sliding piston rod supports are pushed out with the extending hydraulic actuator rod by means of blocks on the extending boom and are restrained from over extending by a telescoping restraint assembly. The support assembly is positioned by means of blocks on the moving section and a slide-tube restraint on the hydraulic cylinder case. No chains, cables or other devices are used to allow one hydraulic actuator to extend or retract more than one section. Since the results of a failure of one or more of the hydraulic actuators is the relatively slow descent of the top end of the boom, the present invention is a safer method of extending the boom sections than conventional methods using chains, cables or the like which are subject to complete sudden failure with possibly violent results. In addition, each hydraulic actuator is protected by a locking valve which prevents inadvertent activation or failure of the actuator. It is therefore the principle aim of the present invention to provide a method of constructing and controlling a new and improved aerial lift, crane or other boom device which meets the foregoing requirements and is capable extending and retracting completely with one linear hydraulic actuator for each moving section.
Another and further object and aim of the present invention is to provide a new and improved aerial lift which meets the foregoing requirements and which includes a stronger hydraulic actuator rod with fixed rigid ends.
Another and further object and aim of the present invention is to provide a new and improved aerial lift which meets the foregoing requirements and which includes a supported hydraulic actuator rod with a sliding support mechanism.
Another and further object and aim of the present invention is to provide a new and improved method of constructing and controlling an aerial lift which meets the foregoing requirements and which is safe to operate.
Other objects and advantages of the invention will become apparent from the Description of the Preferred Embodiments and the Drawings and will be in part pointed out in more detail hereinafter.
The invention consists in the features of construction, combination of elements and arrangement of parts exemplified in the construction hereinafter described and the scope of the invention will be indicated in the appended claims.
REFERENCES:
patent: 3445004 (1969-05-01), Grider et al.
patent: 3807108 (1974-04-01), Johnston
Brahan Thomas J.
Elliott Equipment Company
Lee Philip J.
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