The present invention relates to Caterpillar sidebooms used for pipelaying, and more particularly pertains to methods and apparatus for converting old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms into hydraulically-operated sidebooms, with minimal retrofitting.
It is well known in the art that crawler or tractor-type vehicles having an integrated, rigid maneuverable boom disposed on a side thereof are commonly used for pipelaying operations, i.e., for raising, carrying, and lowering heavy pipe. Referred to as "sidebooms," such vehicles must be capable of safely handling heavy pipe; indeed, there are sideboom models that have been constructed for handling pipe up to 200,000 pounds. Such sidebooms were mechanically-operated in their first incarnation and are now readily available from original equipment manufacturers in hydraulically-operated models.
An early development in the mechanical sideboom art is disclosed by Butterfield et al. in U.S. Pat. No. 3,785,503, wherein a plurality of planetary gears and concomitant shafts are used to drive the winch drums for each of the boom and the load. Primarily due to its inherent complicated, high-maintenance gearing system, no embodiments of the Butterfield sideboom was ever commercialized. A significant improvement in the pipelaying sideboom art would be a sideboom that eliminates all gears to accomplish transmission of power, i.e., that eliminates all mechanical connections between the engine and the winch system.
Other early developments in the sideboom art, albeit not applicable to pipelaying operations, per se, are taught in U.S. Pat. Nos. 2,909,290; and 3,329,283. More particularly, Nichols, in U.S. Pat. No. 2,909,290, teaches a farm tractor-mounted sideboom intended for lifting light loads typical on the farm. Of course, pipelaying operations demand sidebooms with lifting capacities up to 200,000 pounds. Similarly, Wade, in U.S. Pat. No. 3,329,283, teaches a snap mount sideboom configured to be foldable for reducing its prerequisite overhead clearance. Half of the Wade boom's height may be reduced and the folded boom portion secured to the tractor's side by using integral hooks and cable. Especially in view of the Wade sideboom having no counterweight, it should be evident to those skilled in the art that both Wade and Nichols are inapplicable to the rigors of pipelaying wherein not only a strong, firm boom structure is required, but also the framework of the sideboom must be sufficiently broad to provide a low enough center of gravity for stability and must include a counterweight to provide sufficient operational stability and safety. It will be readily understood by those skilled in the art that such attributes are not provided by conventional tractors.
Indicative of initial attempts to improve the sideboom art using hydraulics is an apparatus described by Stefanutti in U.S. Pat. No. 3,265,218. In particular, the use of hydraulically actuated booms and hoist assemblies is described, wherein hydraulic cylinders are used either inside or astride the boom to raise and lower the boom. As will be appreciated by those skilled in the art, the Stefanutti apparatus has not been widely accepted.
As taught by Vinton in U.S. Pat. No. 3,938,669, however, while the introduction of such hydraulically-operated sidebooms were anticipated to provide improvements associated with effectively and safely manipulating winches and cables through an operator's interfacing with clutches, brakes, and levers for controlling the position of the boom and for hoisting and lowering a load, such sidebooms failed to provide the prerequisite control and versatility. To attempt to remedy this deficiency in the art, Vinton discloses a hydraulic circuit that includes two separate sources of hydraulic fluid for controlling sideboom movement-related functions. One fluid source provides low volume hydraulic fluid for accomplishing not only precise, low-speed manipulation and control, but also for preventing anti-drift of both boom and hoist. The other fluid source provides high volume hydraulic fluid for providing high-speed operation of these movement and control functions. The plurality of control valves inherent in the Vinton circuit for controlling the hoist and the boom motors are operated via two levers. This apparatus also incorporates a hydraulic cylinder, instead of a drum/cable arrangement for controlling the boom; no drums or cables are involved in raising or lowering either the boom or the hook, except a short cable connected to the hook at the end of a hydraulic cylinder. As is well known by those skilled in the sideboom art, this methodology was a commercial failure.
As a further development in the sideboom art, Forsyth teaches in U.S. Pat. No. 5,332,110 a hydraulically-operated sideboom intended to prevent boom over-rotation, to impart positive drive to the boom and load winches, and to provide improved control over free fall and vertical kick-out. These safe operating features are particularly intended for pipelaying applications involving lifting and lowering of large pipes. Indicative of current Caterpillar tractors and sidebooms, embodiments taught by Forsyth are exclusively for newly manufactured hydraulically-operated high-drive tractors which are the antithesis of predecessor low-drive mechanically-operated Caterpillar tractors.
As will be appreciated by those skilled in the sideboom art, current Caterpillar hydraulically-operated high-drive sidebooms have a higher center of gravity but operate easier due to less controls than old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms. Such "high drive" models are constructed with an undercarriage that was introduced by Caterpillar in the early 1980's; the sprockets and drive mechanisms for the undercarriage are situated much higher off the ground than the previous conventional "low drive" system that was in effect from the inception of the original Caterpillar sideboom. More particularly, the Caterpillar low-drive sidebooms were discontinued from 1972 through 1986 as follows: model 572E was discontinued in 1972; model 572F was discontinued in 1975; model 572G was discontinued in 1986; model 583H was discontinued in 1974; model 583K was discontinued in 1986; model 594G was discontinued in 1975; and model 594H was discontinued in 1986. In addition, Caterpillar hydraulically-operated high-drive sidebooms are very expensive, and some models not only have inherent counterweight obstruction problems, but also are difficult to move from job-site to job-site. While the Forsyth disclosure teaches that his hydraulic pipelayer is adapted for mounting upon a conventional track-laying tractor (i.e., bulldozer), it is well known in the art that the main frame of a sideboom is constructed differently from that of a conventional tractor. In particular, unlike a conventional tractor which is constructed with an oscillating frame, a sideboom is constructed with a rigid frame of wider track gauge than a conventional tractor. Indeed, Caterpillar identifies such tractor and sideboom frames with different serial numbers series. Thus, to obtain the prerequisite performance demanded in the pipelaying art, a drawworks assembly must be mounted upon a frame capable of rigidity to accommodate the pivoting action of a sideboom typically positioned upon rough terrain, with the frame having a sufficiently wide track gauge for stability purposes.
As will be understood by practitioners in the art, a drawworks system built upon an old, discontinued, mechanically-operated, low-drive, Caterpillar sideboom--having significantly more controls than a conventional discontinued tractor--inherently suffers from a panoply of problems associated with the simultaneous use of a daunting ensemble of gear-shifting mechanisms, clutches, and brakes, all operated by 6 different hand controls to properly lift and manipulate heavy pipes under conditions generally characterized by unpredictable and adverse terrain. Pipeline construction companies constitute 95% of the users of this type of machinery. As will be appreciated by those conversant with the art, historically, such pipeline construction companies have had to choose between the newer high-drive sidebooms with herein before mentioned faults and high price or the older, discontinued Caterpillar sidebooms that are more economical but are more dangerous and are very difficult to operate. It should also be noted that, as the pipelaying industry continues to mature, the number of skilled sideboom operators has gradually diminished.
As should be evident to those skilled in the art, it would be advantageous for construction companies who are continuing to utilize older discontinued Caterpillar sidebooms to have the additional benefits of improved handling, safety, and efficiency. It would be also be advantageous for pipeline contractors to have the ability to expeditiously train low-drive Caterpillar sideboom operators and to simultaneously achieve a level of safety heretofore unmatched by any other sideboom system known in the art, regardless of design. Of course, it would be advantageous for pipelaying contractors to have the benefit of a Caterpillar sideboom that inherently avoids or mitigates the complex levers and the like associated with maneuvering a sideboom, and controlling the lifting and lowering of a pipe load.
Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for effectively and reliably utilizing old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms for pipelaying applications.