Abstract:
A hoist for positioning a load ( 40 ) includes a plurality of lift cylinders ( 15 ), a plurality of position sensors, a plurality of electronically controlled valves, a user input device ( 22 ), and a hoist controller ( 20 ). Each of the hydraulic hoist cylinders is coupled at one end to the hoist and at an opposite end to the load at a lifting point ( 45 ). Each of the position sensors is associated with one of the hoist cylinders and operable to provide position data for the associated hoist cylinder. The electronically controlled valves are hydraulically coupled to the hoist cylinders for extending and retracting the associated hoist cylinders. The user input device is operable by a user to specify load data. The hoist controller is operable to receive the load data from the input device and the position data from the position sensors and in response thereto to control the electronically controlled valves so as to position the load according to the load data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/556,577 filed on Mar. 26, 2004. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     This invention relates generally to hoists for positioning loads during structural fabrication, and in particular, to a hydraulic auxiliary hoist and crane control for high precision load positioning.  
         [0004]     Since the advent of hydraulic jacks or lifting cylinders, construction engineers have had the capability to raise and relocate structures, bridges or buildings of almost any size and tonnage—even entire city centers to allow new underground installations such as subways or essential repair work.  
         [0005]     Weight is not typically a limiting factor in such positioning operations. A greater weight simply requires more cylinders. However, the extent of a straight lift is limited by the plunger stroke length of the cylinders used. Lifting a greater amount than the limiting stroke length typically requires the use of additional holding arrangements to permit the replacement or repositioning of cylinders for the next stage in the lifting operation.  
         [0006]     Using a single crane, a heavy load, such as a large construction segment (roof section, floor section, wall section, large scale architectural ornamentation, bridge section, etc.), can be moved a long vertical distance with relative high speed. However, when precise geometric positioning of the load is required in a vertical and horizontal plane, multiple cranes and elaborate lift rigs are often required. Synchronizing the movements of multiple cranes in this fashion has proved to be difficult and risky. This synchronization difficulty limits the accuracy of the lifting operation and may lead to damage to the load, support fixtures, and/or cranes. Increased risk to the operators and workers is also present in such complicated positioning maneuvers.  
         [0007]     Sudden crane starts and stops create oscillations during the critical stages of the lifting process. Weather conditions also provide a source of disturbances during heavy load positioning applications, as wind can blow a lifted section and thereby induce dangerous side loads on the crane, for which the crane was not designed to bear.  
         [0008]     One system for positioning a load includes a plurality of hydraulic cylinders attached by cables to a crane or other lift mechanism. The hydraulic cylinders are manually controlled to adjust the position of the load. Such manual systems require multiple jogging operations that can induce oscillations. Moreover, the position of only one cylinder it typically changed at a time. This situation can cause the load to become unbalanced.  
         [0009]     Therefore, a need exists for high precision load positioning system that may be implemented without the synchronization and loading issues associated with multiple crane operations or manually controlled lifting cylinders.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     The present invention is directed generally to a hydraulic auxiliary hoist and crane control for high precision load positioning. The hoist includes multiple, synchronized hydraulic hoist cylinders for positioning a load.  
         [0011]     One aspect of the invention is seen in a hoist for positioning a load. The hoist includes a plurality of lift cylinders, a plurality of position sensors, a plurality of electronically controlled valves, a user input device, and a hoist controller. Each of the hydraulic hoist cylinders is coupled at one end to the hoist and at an opposite end to the load at a lifting point. Each of the position sensors is associated with one of the hoist cylinders and operable to provide position data for the associated hoist cylinder. The electronically controlled valves are hydraulically coupled to the hoist cylinders for extending and retracting the associated hoist cylinders. The user input device is operable by a user to specify load data. The hoist controller is operable to receive the load data from the input device and the position data from the position sensors and in response thereto to control the electronically controlled valves so as to position the load according to the load data.  
         [0012]     Another aspect of the present invention is seen where the hoist controller is operable to store geometric data regarding the load and the hoist cylinders and to translate a desired movement of a reference point defined on the load to a position change of at least one of the hoist cylinders to effectuate the desired movement.  
         [0013]     Yet another aspect of the present invention is seen in a crane or other lifting device supporting the hoist cylinders for course positioning of the load, the hoist cylinders being controlled for fine positioning of the load.  
         [0014]     Other objects, advantages and features of the present invention will become apparent from the following specification when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0015]     The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements and in which:  
         [0016]      FIG. 1  is a perspective drawing of a hoist constructed in accordance with the present invention; and  
         [0017]      FIGS. 2 and 3  are simplified diagrams illustrating the geometric relationships of a load positioning operation. 
     
    
       [0018]     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     While the present invention may be embodied in any of several different forms, the present invention is described here with the understanding that the present disclosure is to be considered as setting forth an exemplification of the present invention that is not intended to limit the invention to the specific embodiment(s) illustrated. Nothing in this application is considered critical or essential to the present invention unless explicitly indicated as being “critical” or “essential.” 
         [0020]     Referring now to the drawings wherein like reference numbers correspond to similar components throughout the several views and, specifically, referring to  FIG. 1 , the present invention shall be described in the context of a synchronized hoist  10 . The synchronized hoist  10  includes a plurality of hoist cylinders  15  coupled hydraulically and electrically to a hoist controller  20 . The synchronized hoist  10  is suspended from a hook  25  coupled to a cable  30  extending from a crane  35  or other lifting device. Each hoist cylinder  15  has an associated extension cable  37  coupling it to the hook  25  providing a common center point. The hoist cylinders  15  are coupled to a load  40  at lifting points  45 . Each hoist cylinder  15  is coupled to the hoist controller  20  through hydraulic hoses  50  and a sensor cable  55 . For ease of illustration, only the hoses  50  and cable  55  for a single hoist cylinder  15  are numbered. Although four hoist cylinders  15  are illustrated, the application of the present invention is not limited to any particular number of cylinders. For example, two-point, three-point, six-point, etc., configurations may be used. The routing of the hoses  50  and cables  55  illustrated is provided for illustrative purposes to show the connections between the components, and not intended to represent an actual routing. In an actual implementation, bundles or other management techniques may be used to route the hoses  55  and cables  55 , and some cables  55  may be shared.  
         [0021]     In the illustrated embodiment, the hoist cylinders  15  are equipped with electrical stroke sensors that measure the exact plunger travel of the associated cylinder. Position information from the stroke sensor is provided to the hoist controller  20  over the sensor cable  55 . Hence, the position and/or movement of all lifting points  45  can be simultaneously monitored and synchronously controlled. An exemplary type of stroke sensor is a linear variable differential transformer (LVDT).  
         [0022]     The synchronized hoist  10  allows high precision load positioning with only a single crane  35 . Course positioning of the load  40  may be accomplished by the crane  35 . By controlling the individual positions of the hoist cylinders  15 , the hoist controller  20  can precisely maneuver the load  40  in both a vertical and a horizontal plane. Course positioning with the crane  35 , followed by fine positioning using the synchronized hoist  10  avoids the need to use crane jogging (i.e., sudden starts and stops of the crane  35 ), which have the potential to cause oscillations of the wire rope and premature wear of the crane brakes. Also, because the hoist cylinders  15  are synchronously controlled by the hoist controller  20 , manual jogging of the hoist cylinders  15  is avoided.  
         [0023]     Although, the hoist controller  20  is illustrated as a remote unit, it may be integrated with the crane  35 . Hence, positioning of the load  40  may be managed from the crane  35  by the crane operator or by other operators near the installation site for the load  40  using a remote unit.  
         [0024]     The hoist cylinders  15  are precisely electronically controlled by the hoist controller  20  in their extension. In the illustrated embodiment, the hoist cylinders  15  are double-acting pulling cylinders. The double-acting function allows precise control of both lifting and lowering adjustments in each extension cable  37 . The illustrative hoist cylinders  15  have a maximum hydraulic pressure of 700 bar. The pulling capacity of the hoist cylinders  15  depends on the type of application. However, the maximum load is limited by the lifting capacity of the cables  30 ,  37 , not by the hydraulic system. Hoist cylinders  15  having plunger strokes of approximately 1500 mm may be used in hoisting and positioning applications with 4 or 6 lifting points  45 .  
         [0025]     The type of unit used for the hoist controller  20  may vary, depending on the particular application. For example, the hoist controller  20  may be implemented using a programmable logic controller (PLC) or a general purpose computer programmed with software to implement the load positioning functions. For example, the hoist controller  20  may be implemented using logic similar to that used in an SLCPC-2001 series controller (PC controlled synchronous lift system) offered by Enerpac, an Actuant company having a place of business in Glendale, Wis.  
         [0026]     In general, the hoist controller  20  is programmed by an operator via a user input device  22  (e.g., a keyboard and display integrated with or attached to the hoist controller  20 ) with load data associated with the load  40  and hoist arrangement. For example, the load data may include user instructions associated with load movements, load material, load geometry, lifting point geometry, etc. The hoist controller  20  manages one or more electronically controlled valves  58  for controlling the supply of hydraulic fluid to either side of the pistons in the hoist cylinders  15 . The processing device used to implement the logical functions of the hoist controller  20  may be remote from the mechanical system and the valves  58  used to control the positioning of the hoist cylinders  15 . A hardwired or wireless connection may be used for communication between the logical and mechanical portions of the hoist controller  20 , however, for ease of illustration the hoist controller  20  is shown as a single integrated unit.  
         [0027]     The precision provided by the hoist cylinders  15  allows the synchronized hoist  10  to be used in a variety of applications, such as high accuracy relocating, pre-programmed relocating, pre-programmed twisting or turning, and counterweighing (i.e., determining the center of gravity. Exemplary applications include, but are not limited to positioning of roof sections, concrete elements, steel structures, etc. in the construction industry; precise positioning of turbines, transformers, fuel rods, etc. in the utility industry; precise machinery loading, mill roll changes, bearing changes, etc. in the heavy equipment industry; precise positioning of pipe lines, blow out valves, etc. in the petrochemical and oil and gas industry; and relocating and positioning of ship segments in shipbuilding industry.  
         [0028]     In some applications additional sensors and or activators may be included in the synchronized hoist  10  to facilitate a higher degree of load control. In one embodiment, the pressure in each hoist cylinder  15 , or the force exerted on each hoist cylinder  15 , can also be monitored by the hoist controller  20 . For example, a sensor  60 , such as a load sensing cell or a pressure transducer, may be associated with each hoist cylinder  15 , to sense the loading on each hoist cylinder  15 . Loading Information from the sensor  60  may be communicated to the hoist controller  20  over the sensor cables  55 .  
         [0029]     The hoist controller  20  may use loading information from the sensors  60  to balance the load, or to instantaneously, or nearly instantaneously, correct for weather related abnormalities. Additional information regarding weather conditions may be obtained by providing a deflection angle sensor  65  with an associated sensor cable  67  on the crane  35  that indicates the deflection of the cable from vertical (e.g., due to wind). For example, if a wind blows a load sideways, the hoist controller  20  can extend or retract the hoist cylinders  15  to present the smallest possible area for the wind to blow against, to balance the load, or to adjust the hoist cylinders  15  to retain the orientation of the load  40  relative to the structure in which the load  40  is being installed.  
         [0030]     The hoist controller  20  may use load information from the sensors  60  and the position information from the hoist cylinders  15  to determine the center of gravity of the load  40 . The loading and position information may be resolved into force vectors that allow the characterization of the load  40 . The center of gravity information may be used by the hoist controller  20  in determining the adjustments for the hoist cylinders  150  necessary to position the load  40 .  
         [0031]     The loading capacity limits of the crane  35  may also be programmed into the hoist controller  20  so that the hoist controller  20  may signal an overloading alert condition or automatically make preventative adjustments to the hoist cylinders  15  if the capacity limits of the crane  35  are approached.  
         [0032]     Another auxiliary device that may be provided to provide additional information and control functionality for the synchronized hoist  10  is a hydraulic rotary coupling  70  coupled to the cable  30  (e.g., above the hook  25 ). The rotary coupling  70  may be equipped with an electronic angle sensor indicating the rotational position of the rotary coupling  70  about a vertical axis. An additional hydraulic hose  75  and sensor cable  80  may be provided connecting the rotary coupling  70  to the hoist controller  20 . The hoist controller  20  may control the angle of the rotary coupling  70  based on the information from the angle sensor. The rotary coupling  70  provides an additional axis of control to aid in high precision positioning of the load  40 .  
         [0033]     The hoist controller  20  may be programmed to automatically determine position changes for the hoist cylinders  15  to effect the positioning of various reference points on the load  40 . For example, reference points  85 ,  90 ,  95 ,  100  may be defined on the load  40  independent from the position of the lifting points  45 . An operator may input to the hoist controller  20  load data, such as the shape, weight or material, and other information that describes the load  40 , the position of the lifting points  45 , and the position of the reference points  85 ,  90 ,  95 ,  100 . In some cases, one or more of the reference points may directly correspond to one or more of the lifting points  45 . Formulas or look-up tables can then be programmed into the hoist controller  20  so that the operator can input a specific movement to the hoist controller  20  with respect to one or more of the reference points  85 ,  90 ,  95 , 100 . For example, the operator may request that the load  40  at reference point  100  be moved down a certain distance. The movement may also be coordinated with a different reference point. For example, move the load  40  at reference point  100  down a predetermined distance without changing the position of reference point  90 . Since the movement of the load  40  by the hoist cylinder  15  associated with reference point  100  may cause the load to rebalance in a different position, an iterative process may be needed to achieve the final position. The hoist controller  20  may complete the iterative process prior to moving the hoist cylinders  15 , and execute the movements once a solution is obtained.  
         [0034]     The hoist controller  20  may also be programmed with instructions for completing more complex movements, such as moving the positions of all four reference points  85 ,  90 ,  95 ,  100  of the load  40  at the same time. The hoist controller  20  can then calculate how much each of the four hoist cylinders  15  must be extended or retracted to effect the requested movement, and operate the hydraulic control valves to effect the position change. While moving the hoist cylinders  15 , the hoist controller  20  may monitor the position sensor associated with each hoist cylinder  15  to retain feedback control over the positioning operation.  
         [0035]     Due to the geometry of the synchronized hoist  10 , the relationships between the lifting points  45  and the reference points  85 ,  90 ,  95 ,  100  may be defined using triangles with known dimensions.  FIG. 2  illustrates an exemplary geometric relationship for a synchronized hoist  10  with two hoist cylinders  105 ,  110  and their associated lifting points  115 ,  120 . Sides A and B represent the combined lengths of the hoist cylinders  105 ,  110  and their associated extension cables  37 . The side C represents the fixed distance between the lifting points  115 ,  120 . Side D represents the distance between a reference point  125  and the hook  25 . Side E represents the fixed distance between the lifting point  115  and a reference point  125 . The hoist controller  20  can determine A and B based on the length of the extension cables  37  and the position of each of the hoist cylinders  105 ,  110 .  
         [0036]     The geometric relationships between the lifting points  115 ,  120  and the reference point  125  are known Since C is fixed, the hoist controller  20  can calculate the value of the unknown sides and angles known trigonometric relationships, such as the sine rule: 
 
 A /sin( a )= B /sin( b )= C /sin( c )   (1) 
 
         [0037]     and the cosine rule: 
 
 B   2   =A   2   +C   2 −2  AC  cos( b )   (2) 
 
         [0038]     Changes to the lengths of the sides A and B due to the movement of one or more of the hoist cylinders  105 ,  110  affect the angles (e.g., a, b, c, d) and the lengths of certain sides (e.g., D) of the composite geometry. The effects of these changes can be readily determined using these known trigonometric relationships. For example,  FIG. 3  illustrates the changed geometric relationship after the position of the hoist cylinder  105  is changed, as designated by A′. As a result of this change, the angles a′, b′, c′, d′ and lengths, D′ also change. Values for these changed parameters of the geometry may be determined in advance by the hoist controller  20  to translate a desired position change into a solution for synchronously moving the hoist cylinders  105 ,  110 .  
         [0039]     Returning to  FIG. 1 , as the number of hoist cylinders  15  increases, the number of triangles needed to represent the geometric arrangement increases, but the unknown values may still be determined using the known positions of the hoist cylinders  15  and the trigonometric relationships between the lifting points  45  and the reference points  85 ,  90 ,  95 ,  100 .  
         [0040]     Turning now to  FIG. 4 , a diagram illustrating an alternative embodiment of the synchronized hoist  10  is provided. Rather than the hook  25  serving as a center member, the synchronized hoist  10  further includes a frame  150  from which the extension cables  37  and hoist cylinders  15  extend. For ease of illustration, portions of the lifting system (e.g., the hoist controller  20 , crane  35 , hoses  50 , cables  55 , etc.) are omitted. The extension cables  37  and hoist cylinders  15  are attached to corners  155  of the frame  150 . The frame  150 , in turn, may be coupled by additional cabling to the hook  25 . The use of the frame  150  as the center member changes the effects of movement of the hoist cylinders  15  on the movement of the load  40 . Because the hoist cylinders  15  are closer to being perpendicular to the load  40  as compared to the embodiment of  FIG. 1 , movement of the hoist cylinders  15  more closely translates to vertical movement of the load  40  (i.e., the vertical component of the lifting vector is increased relative to the horizontal component. Other type of center members may be used depending on the number of hoist cylinders  15  employed and the geometry of the load  40 .  
         [0041]     The synchronized hoist  10  of the present invention provides numerous advantages. Because multiple cranes are not required, to achieve high precision positioning, the cost of the operation is reduced, the operating speed is increased, and the risk to the operators is decreased. Positioning precision is increased due to the simplification in the synchronization required to position the load. Moreover, the effects of weather conditions on the effectiveness of the positioning may be reduced, as the load can be reoriented to compensate for and minimize the effects of wind. Because the hoist controller  20  synchronously controls the lift cylinders  15  based on the programmed load data, the smoothness of the positioning operation is increased.  
         [0042]     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.