Patent Abstract:
A pipelayer providing higher lifting capacities without adding weight or size to an undercarriage or boom of the pipelayer is disclosed. The pipelayer is designed and sized to have a maximum lifting capacity when the boom is extended from the undercarriage a predetermined, relatively short distance. However, in use the boom often needs to extend further away from the undercarriage, and in so doing the lifting capacity of the pipelayer decreases. The present disclosure provides additional lifting capacity in that extended range by selectively deploying a counterweight away from the undercarriage once the boom is extended past the predetermined distance. In so doing, not only is the lifting capacity of the pipelayer increased, but the size and weight of the undercarriage and boom are not increased. This enables standard sized undercarriages and other supporting structure to be used, thereby aiding in maneuverability and shipping of the pipelayers, while at the same time reducing manufacturing and usage costs.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a non-provisional application claiming priority under 35 USC §119 (e) to U.S. Provisional Patent Application No. 61/249,828 filed on Oct. 8, 2009. 
     TECHNICAL FIELD 
     The present disclosure generally relates to construction vehicles and, more particularly, relates to pipelayers. 
     BACKGROUND 
     Pipelayers are specialized vehicles used for installing large, heavy lengths of conduit into or above ground. Such conduits may be used, for example, to carry oil and gas from remote well locations over vast distances to a receiving station or refinery. In so doing, transportation costs for shipping, trucking or otherwise moving the oil and gas can be avoided. In addition to petroleum pipelines, pipelayers can also be used to install piping for other materials, or for installing of drain tile, culverts or other irrigation and drainage structure. 
     However, the installation of such pipelines is often very challenging. The locations of such oil and gas wells are commonly some of the most remote areas on earth, and the terrain over which the pipeline must traverse is often some of the most rugged. The climate of the installations can have very high or very low temperatures. The land may have significant elevational changes, and be subject to mudslides, severe weather, deep forestation and the like. In order to install the pipe, the pipelayer must be able to operate in all of the above-climate conditions, navigate over such terrain, and still be able to lift loads often in excess of 200,000 pounds. 
     Not only must pipelayers be able to handle such tasks, but given that the pipes are installed in long segments welded or otherwise secured together, they must be installed with great precision. The ends of the pipe being welded together must butt up against each other within a very tight tolerance. In addition, the pipes are often installed in connected fashion. This can result in a very long length of conduit (sometimes exceeding a mile) which must be laid into the ground in coordinated fashion. A series of pipelayers in such a situation will therefore be called upon to work in concert to lay the pipe. 
     When installing pipelines, if a natural or pre-made easement does not exist, a path through the terrain is first cleared through the forest, mountain pass or other geographical challenge at hand. A trench is then dug to the desired size, which is typically many feet deep and many feet wide. A right-of-way is also provided to one or both sides of the trench to allow for passage of trucks to transport the pipe into the location, and for passage of pipelayers to install the pipe. This right-of-way is ideally flat and sufficiently wide to easily accommodate the pipelayer but given the constraints imposed by the area topography and space availabilities of the local region or country, this may not always be the case. Pipelayers therefore often need to carry not only very heavy loads, but do so without being on level, stable ground. 
     Current pipelayers typically work on a track-type undercarriage and operate with a side-boom that can be extended at a variable angle to the chassis of the pipelayer. A cable is trained from a winch or other power source through a series of pulleys and terminates in a grapple hook or other suitable terminus. The grapple hook or other suitable terminus can then be secured to the pipe in such a way that when the winch recoils, the pipe is lifted. The boom arm is then extended and the pipelayer itself is navigated to a desired location for accurate installation of the pipe. 
     While effective, it can be seen that the weight of the pipe is positioned in cantilevered fashion away from the chassis, engine and undercarriage of the pipelayer. As the chassis, engine and undercarriage comprise the majority of the weight of a pipelayer, depending on the weight of the pipe being lifted and the length of the boom arm, the pipelayer can be subject to potential tipping and instability. Conversely, if the pipelayer is to be maintained in a stable position, the ability of the pipelayer to access the desired installation location can be significantly limited. 
     To offset these concerns, current pipelayers typically include a counterweight. The counterweight may comprise a series of heavy plates secured to a hinged structure such that through the use of a hydraulic cylinder or the like, the counterweight can be swung away from the chassis of the pipelayer on the side of the pipelayer opposite to the boom and thus counterbalance the weight of the load being lifted. 
     However, the counterweight systems of currently available pipelayers are operated entirely at the discretion of the operator and thus are arbitrarily applied. The operator of the pipelayer is able to extend the counterweight as he or she sees fit without regard to optimizing lifting capacity or stability of the pipelayer. Often, the counterweight is simply extended and left in that position during operation of the pipelayer. The lifting capacity and possible boom angle are therefore largely limited by such a fixed system. 
     Current demands being placed on pipelayer design, moreover, are requiring higher lifting capacities and boom lengths/angles. The pipelayer could in theory simply be made larger and heavier to satisfy these needs, but realistically the general footprint of the pipelayer is limited by cost, maneuverability, and transportation considerations. As stated above, pipelayers need to be operated in very remote and difficult locations. Once built, they need to be sent by rail and/or truck for use, and thus the size of those rails and trucks limit the upper end in terms of dimensions of overall pipelayer design. Even if they could be shipped to the location, they also have to be nimble enough to perform the job. Moreover, over-sizing the undercarriage and boom of the pipelayer will also increase manufacturing costs in terms of materials, and operating costs in terms of fuel. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the disclosure, a pipelayer is therefore disclosed which comprises an undercarriage, a boom movable relative to the undercarriage, and a counterweight movable relative to the undercarriage ranging between fully deployed and fully retracted positions, the counterweight being movable to the fully deployed position only when the boom has extended a predetermined distance from the undercarriage. 
     In accordance with another aspect of the disclosure, a method of operating a pipelayer is disclosed, which comprises extending a boom away from an undercarriage, measuring the distance the boom is extended away from the undercarriage, and deploying the counterweight only when the measured distance is greater than a predetermined length. 
     In accordance with a further aspect of the disclosure, a heavy lift assembly for a pipelayer is disclosed which comprises a position sensor adapted to measure a parameter indicative of the distance a boom is extended away from an undercarriage of the pipelayer, a processor receiving the measured parameter signal indicative of boom extension distance from the position sensor, and an operator interface connected to the processor and provided with an input device through which an operator can engage the heavy lift assembly, wherein the input device is actuable only when the boom has extended away from the undercarriage by a predetermined distance. 
     In accordance with a still further aspect of the disclosure, in a pipelayer having an undercarriage, chassis and boom weight of A and a machine maximum lifting capacity of B, a heavy lift attachment is disclosed which is adapted to increase the machine maximum lifting capacity to a value greater than B within a heavy lift operating range while maintaining the machine weight as A. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of pipelayer constructed in accordance with the teachings of this disclosure; 
         FIG. 2  is a front view of a pipelayer relative to a trench in which pipe is being laid, and with a boom of the pipelayer extended to a distance providing the pipelayer with maximum lifting capacity; 
         FIG. 3  is a front view of the pipelayer similar to  FIG. 2 , but showing the pipelayer boom extended to a normal operating distance and causing the pipelayer to start to tilt; 
         FIG. 4  is a front view of the pipelayer similar to  FIG. 3 , but showing a heavy lift attachment of the pipelayer deployed to counterbalance the load being lifted 
         FIG. 5  is a flowchart depicting a sample sequence of steps which may be practiced according to the method of the present disclosure; 
         FIG. 6  is a schematic representation of the present disclosure; 
         FIG. 7  is a chart depicting the lift curve of a conventional pipelayer; and 
         FIG. 8  is a chart similar to  FIG. 7 , but showing the improved lift curve of a pipelayer constructed in accordance with the teachings of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and with specific reference to  FIG. 1 , a pipelayer constructed in accordance with the present disclosure is generally referred to by reference numeral  100 . While the following detailed description and drawings are made with reference to a pipelayer, it is important to note that the teachings of this disclosure can be employed on other earth moving or construction machines including, but not limited to, loaders, back-hoes, lift-trucks, cherry-pickers, forklifts, excavators, or any other movable vehicle where a load is being lifted at a distance from the main body of the vehicle. 
     The pipelayer  100  may include an undercarriage  102  comprised of first and second drive tracks  104 ,  106  supporting a chassis  108 . A power source, typically a diesel engine,  110  is supported by the chassis  108 . An operator seat  112  and control console  114  may also be supported by the chassis  108  from which the operator can control one or both tracks  104  and  106  to drive the pipelayer  100  forward, backward and turn. Each of the tracks  104 ,  106  may be composed of a series of interlinked track shoes  116  in an oval track or high drive configuration. As shown, the tracks  104 ,  106  may be trained around first and second idlers  118 ,  120  supported by a track roller frame  119 , a sprocket  121 , as well as a series of other rollers  122  in a high-drive configuration. 
     Extending relative to the undercarriage is a boom  124 . The boom  124  may include first and second legs  126 ,  128  independently hinged to the undercarriage  102  at a base  130 , and which terminate at a joined tip  132 . The boom  124  may be up any length desired, with up to twenty-eight or more feet long being suitable. A lifting cable(s)  134  extends from a winch  136  through a series of sheaves  138  at the boom tip  132  and terminates in a grapple hook  140 , vacuum lift (not shown) or are other suitable arrangement for wrapping around or otherwise securing to a pipe  142  ( FIGS. 2-4 ) to be lifted. 
     In operation,  FIGS. 2 and 3  show that the pipelayer  100  is typically navigated by tracks  104 ,  106  to be adjacent a trench  144  pre-dug into ground  145 . More precisely, the pipelayer  100  should be positioned away from the trench  144  according to applicable regulations. Once in such a position, the boom  124  may be extended away from the undercarriage  102  to facilitate lifting the pipe  142  and laying same into the trench  144 . For the purposes of this disclosure, the distance that the boom  124  is extended away from the undercarriage  102 , specifically the distance the tip  132  is extended away from the roller  122 , will be referred to as overhang  146 . 
     However, as shown in  FIG. 2 , the pipelayer  100  has its greatest lifting capacity when the boom  124  is extended away from the undercarriage  102  by an overhang  146  of zero to four feet. This distance gives the pipelayer its shortest tipping point, and thus the counterweight its maximum mechanical advantage. Current pipelayers are provided with myriad different lifting capacities, with 40,000; 90,000; 140,000 and 200,000 pound lifting capacities being examples. However, with the direction of the industry gaining momentum to put larger, heavier pipe in the ground, machines with even larger lifting capacities are desired. Regardless of the maximum lifting capacity of the given pipelayer, it is to be understood that the entire pipelayer  100 , including the undercarriage  102 , boom  124 , and engine  110 , as dictated by current ISO (International Organization for Standardization) standards need to be designed and engineered to handle that load. This is true even though that maximum lifting capacity is not often called for, the importance of which will be discussed in further detail herein. 
     Referring now to  FIG. 3 , it will be seen that the boom  124  has been extended to a much greater overhang  146 . In fact, in such a position the weight of the pipe  142 , length of the boom  124  and the overhang  146  may create a moment great enough to overcome the weight of the pipelayer undercarriage  102 , engine  104  and associated machinery, and thereby start to cause the pipelayer  100  to tilt. As a result of this and other factors, in the position of  FIG. 3 , the lifting capacity and stability of the pipelayer  100  are significantly diminished. However, given the diameter of the pipe  142  and the relative dimensions of the trench  144  and pipelayer  100 , the operator has no choice but to extend the boom  124  to an overhang  146  at which the lifting capacity and stability of the pipelayer  100  are less than maximum. In other words, as the pipe  142  may itself have a diameter of, for example, three or four feet, and the pipelayer  100  is required to be a minimum of the depth of the trench  144  away from the trench  144 , the overhang  146  of the boom  124  in normal operation is may be well past the point of maximum lifting capacity. 
     In order to offset the moment created in  FIG. 3 , a counterweight  148  can be extended in a direction laterally opposite to the boom  124  as shown best in  FIG. 4 . The counterweight  148  may be comprised of a series of heavy plates  150  (see  FIG. 1 ) secured to a counterweight frame  152 . The counterweight frame  152  may be hingedly attached to the undercarriage  102  and/or chassis  108  and be movable between the retracted position of  FIGS. 2 and 3 , and the deployed position of  FIG. 4 , or anywhere in between by way of a hydraulic cylinder  154  or the like. In so doing the center of gravity of the pipelayer  100  is moved laterally away from the trench  144 , thus balancing the pipelayer  100 . 
     However, while this approach is effective, it has significant practical limitations. In theory, if the lifting capacity of the pipelayer  100  is to be increased, the overall size of the undercarriage  102 , length and strength of the boom  124 , horsepower of the engine  110 , power of the hydraulic system  154  and winch  136  can all be increased to supply the lifting capacity needed. In practice however, this could easily result in a pipelayer which is either too big to manufacture cost-effectively, too big to ship on existing rail systems and roadways, too bulky to maneuver on the challenging terrain mentioned above, or too expensive to operate in terms of fuel consumption. 
     The present disclosure therefore sets forth an apparatus and method by which the lifting capacity of the pipelayer  100  is increased without increasing the size or cost of the undercarriage  102 , boom  124 , engine  110  or the like. The present disclosure does so by, among other things, providing additional counterweight  148 , but only allowing deployment of the counterweight  148  after the boom  124  has been extended a predetermined distance. More specifically, the pipelayer  100  monitors the position of the boom  124  and enables deployment of the counterweight  148  in a smart, closed-loop fashion. A heavy-lift attachment (HLA)  156  may be used to do so as either part of a newly constructed pipelayer  100  or as a retrofit to existing pipelayers. As used herein, HLA is defined as a collection of components which can be added to a pipelayer  100  to increase the lifting capacity of the pipelayer across a predetermined overhang range without increasing the size of the undercarriage  102 , chassis  108 , boom  124 , or engine  110 . 
     As shown in  FIG. 6 , the HLA  156  may include a position sensor  158  which measures a parameter indicative of the overhang distance  146 . The sensor  158  may be provided in any number of forms including, but not limited to, an encoder provided on a rotating shaft of the boom or winch, a rotary sensor, a magnetic sensor, a proximity switch or the like. One of ordinary skill in the art will understand the various types of sensors which can be used to monitor the angular position of the boom  124  or overhang distance  146  and generate a signal indicative of same. 
     As shown in  FIG. 6 , the HLA  156  may also include a processor  160  electronically communicating with the position sensor  158 , and an enable/disable/automatic switch  162  also in communication with the processor  160 . The enable/disable/automatic switch  162  may be integrated into an existing operator interface  164  on the control console  114  such as with a control screen or the like, or may be provided as a stand-alone switch added to the control console  114 . The HLA  156  may also include software  166  electronically stored in a memory  168  also in electronic communication with the processor  160 . The operator may also be given the opportunity to have the processor  160  automatically control the HLA  156 . 
     In operation, the pipelayer  100  may work as set forth in the flowchart of  FIG. 5 . As shown, the operator would navigate the pipelayer  100  to be adjacent the trench  144  with the pipe  142  secured to cable  134  as shown by a step  170 . The boom  124  would then be extended (step  172 ) away from the undercarriage  102  to an overhang distance  146  at which the radial center of the pipe  142  is directly over the centerline of the trench  144 . The winch  136  would then be operated to lower the pipe  142  into the trench  144  (step not shown in  FIG. 5 ). 
     As the boom  124  is being extended, the position sensor may continually monitor the overhang distance  146  and decide as in step  174  if the overhang distance  146  is greater than the predetermined distance at which the pipelayer  100  enters a heavy-lift operating range  176  (see  FIG. 8 ). As indicated above, this range is typically from six to twenty feet of overhang  146 , but may be anywhere from four to twenty-eight feet (or more if the boom  124  is longer than twenty-eight feet). Ensuring the boom  124  is extended far enough so that the pipelayer  100  is in the heavy-lift operating range  176  is important because if the boom  124  is closer to the undercarriage  102 , extension of the counterweight  148  at that time could potentially increase the maximum lifting capacity of the pipelayer  100  beyond its overall rating and thereby require the undercarriage  102 , chassis  108 , boom  124 , and all associated machinery to be increased in size and strength to handle that increased load. As indicated above, as it would be desirable to use a conventionally sized undercarriage and other supporting structure, disabling the HLA  156  when the boom  124  is not in the heavy-lift operating range  176  satisfies both needs. 
     Referring again to  FIG. 5 , if the overhang distance  146  is in the heavy-lift operating range  176 , the processor  160  will send a signal to the enable/disable/automatic switch  162  or other operator interface  164  informing the operator that heavy-lift capability is available as shown in step  178 . If the overhang distance  146  is not in the heavy-lift operating range  176 , the enable/disable/automatic switch  162  is not enabled as shown by step  180 . Alternatively, the processor  160  may automatically keep the HLA  156  on or off. 
     Once heavy-lift capability is available, the operator can be provided with the option of engaging same as shown by step  182 . If so, the processor  160  causes the hydraulic cylinder  154  to extend the counterweight  148  as shown in a step  184 . The counterweight  148  may be fully deployed or be positioned to a distance to most effectively offset the moment created by the extended boom  124  and load supported by the extended boom  124 . In addition to, or as an alternative to, adjusting the relative deployment position of the counterweight  148 , the counterweight  148  can be hinged or separately provided to only deploy the weight needed to counteract the aforesaid moment. For example, if the counterweight  148  is provided in a series of plates  150  or other masses, less than all the counterweight  148  can be deployed. 
     Once deployed, the pipelayer  100  may continually monitor (as shown in a step  186 ) the overhang distance  146  to determine if it the boom  124  has retracted to a point where the pipelayer  100  is no longer in the heavy-lift operating range  176 . If so, the processor  160  may cause the counterweight  148  to automatically retract as shown in a step  188 . 
     By providing such a system, the pipelayer  100  of the present disclosure is able to greatly increase its maximum lifting capacity across a large portion of its operating range. This is best shown in a comparison of  FIGS. 7 and 8 .  FIG. 7  depicts a load curve for a prior art pipelayer listing the maximum lifting capacity on the vertical axis, and the overhang distance on the horizontal axis. As can be seen the pipelayer has its maximum lifting capacity (200,000 lbs. in the depicted embodiment) at an overhang distance of four feet. As the overhang distance increases it drops precipitously until reaching its minimum lifting capacity (25,000 lbs. in the depicted embodiment) at an overhang distance of twenty-eight feet. 
     However, as dramatically shown in  FIG. 8 , the maximum lifting capacity of the pipelayer  100 , using the same size undercarriage  102  and engine  110  as the prior art example, may be increased by as much as 15% percent or more at all overhang distances  146  supported by the HLA system. In fact, the maximum lifting capacity at four feet of overhang  146  has been increased to roughly 230,000 pounds. Moreover, as it desirable to employ conventionally sized undercarriages  102  and other support structure, the pipelayer  100  of the present disclosure disables the HLA  154  until the overhang  146  has entered the heavy-lift operating range  176 . The heavy lift operating range  176  differs depending on the size of the pipelayer  100 , but is typically at a distance at which the lifting capacity of the pipelayer  100 , even with the HLA deployed is still at or below the maximum lifting capacity of the pipelayer  100 , thus enabling the load to be lifted without over-sizing or re-engineering the undercarriage  102  and other supporting structure of the pipelayer  100 .  FIG. 8  shows that the heavy-lift operating range  176  extending from eight feet to twenty-eight feet, but as indicated above, depending on design characteristics of the given pipelayer, the heavy-lift operating range  176  may be six to twenty feet, or anywhere from four feet to the entire length of the boom (twenty-eight feet in the depicted embodiment). 
     Couching the two curves of  FIGS. 7 and 8  in machine production terms, two exemplary models of pipelayers manufactured by the present assignee have maximum lifting capacities of roughly 200,000 pounds and 230,000 pounds, respectively. Those pipelayers have overall machine weights of roughly 117,000 pounds, 151,000 pounds, respectively. By utilizing the teachings of the present disclosure, a pipelayer having roughly the size and weight of the smaller machine can now be produced having the ability to perform the same work as the larger machine in the working range. The foregoing data is of course only one example, and other sized machines and savings are possible within the scope of this disclosure. Nonetheless, from this example it can be seen that compared to conventional pipelayers having an undercarriage, chassis and boom weight of A, and a maximum lifting capacity of B, the present disclosure allows a pipelayer to be manufactured with an a maximum lifting capacity across the heavy lift operating range that is greater than B and at least as high as 1.15B, while still maintaining the weight as A. Moreover, not only can new pipelayers be built in this fashion, but by utilizing the HLA, existing pipelayers can be retrofit to have this added power as well. 
     While the maximum lifting capacity B of the pipelayer  100  is increased by the teachings of this disclosure, it is important to understand that the present disclosure disables the HLA  154  at cut-off  190  as shown in  FIG. 8 . In other words, even though the HLA could in theory be used to extend the maximum lifting capacity of the pipelayer  100  across the entire overhang range of 0-28 feet in the depicted curve, the HLA is only engageable across the heavy lift operating range  176 . As shown, this results in a transition to a new curve which begins at cut-off  190  and extends to the maximum overhang point  192  of  FIG. 8 . The portion of the curve depicted in  FIG. 8  for overhangs of four to eight feet is only provided to show the potential lifting capacity if the HLA were not disabled at the cut-off  190 . If the HLA were not disabled once the overhang  146  dropped below the cut-off  190 , the operator might try to lift a load which was beyond the maximum lifting capacity for which the undercarriage  102  is designed and result in structural damage to the pipelayer. By limiting the use of the HLA  154  to the heavy lift operating range  176 , and disabling the HLA once the overhang  146  is less than the cut-off  190 , the operator is able to lift a greater load across the relatively wide range of overhangs defined by the heavy lift operating range  176 , without damaging the pipelayer  100  or requiring the pipelayer  100  to be manufactured with a larger undercarriage  102  to handle that load. 
     INDUSTRIAL APPLICABILITY 
     From the foregoing, it can be seen that the technology disclosed herein has industrial applicability in a variety of settings such as, but not limited to, increasing the lifting capacity of pipelayers without over-sizing or increasing the size of the undercarriage, engine, boom or other structures of the pipelayer. The pipelayer does so by providing additional counterweight, monitoring the position of the boom overhang, comparing that to the maximum load curve stored in memory, and only when the overhang distance increases to a point at which the resulting lifting capacity of the pipelayer is at or below the overall maximum lifting capacity, does the pipelayer allow a heavy lift attachment to deploy the counterweight. Deployment of the counterweight offsets the moment created by the extended boom and attached load of the pipe, thereby balancing the pipelayer while at the same time increasing its lifting capacity across a majority of its operating range. 
     While the foregoing has been made with primary reference to a pipelayer, it is to be understood that its teachings can be employed to increase the operating range of any number of similar vehicles including, but not limited to, loaders, excavators, lift trucks, cherry pickers, back-hoes, fork-lifts, or any other movable vehicle where a load is being lifted at a distance from the main body of the vehicle and thereby creating a moment tending to tip the vehicle.

Technology Classification (CPC): 1