Patent Publication Number: US-6213318-B1

Title: Rotatable connection system for crane boom sections

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to lift cranes, and more particularly to rotatable connection systems for sectional boom members for cranes and the like. 
     Large capacity lift cranes typically have elongate load supporting boom structures comprised of sectional boom members secured in end-to-end abutting relationship. Predominantly, each of the sectional boom members is made of a plurality of generally disposed lacing or lattice elements. The terminal end portions of each chord are generally provided with connectors of one form or another to secure abutting boom segments together and to carry compressive loads between abutting chords. Typical connectors comprise male and female lugs secured by a pin carrying compressive loads in double shear. 
     An example 220 foot boom may be made of a 40 foot boom butt pivotally mounted to the crane upper works, a 30 foot boom top equipped with sheaves and rigging for lifting and supporting loads, with five sectional boom members in between: one 10 feet in length, one 20 feet in length and three 40 feet in length. Such an example boom has six boom section connections. Typically each section has four chords, and hence four connectors, making a total of 24 connectors that must be aligned and pinned to assemble the boom. 
     Large capacity cranes require very large boom cross sections. As a result, even when the boom segments are laying flat on the ground, the pin connectors between the top chords are typically eight feet or higher off the ground. The rigging personnel must either move a step ladder to each pin location or stand and walk along the top of the boom to reach the top connectors. 
     A 40 foot long sectional boom member may weight over 5,000 lbs. Thus, an assist crane is required to lift the boom member. One rigger usually then holds the suspended boom section in general alignment while a second rigger uses a large hammer (10 or 15 lbs.) to manually drive the pin, which typically has a long taper, into position. In the prior art, the pins connecting the boom sections are generally used to carry the compressive loads between chords. As a result, the pins have a tight fit, further increasing the difficulty in assembling the boom. As such, it may take three men (a crane operator and two riggers) four or more hours to assemble the example 220 foot boom. Where the crane is moved frequently, the costs to assemble and disassemble the boom may exceed the cost to lift and position the load for which the crane is used. 
     Efforts have been made to design sectional boom members with quick-connect systems. For example, U.S. Pat. No. 3,511,388 discloses a pin connection system for boom structures having tubular chord members. Tapered male lug members are disclosed for insertion, presumably with some rapidity, into female sockets. The lugs are then held together by a pin. Compressive loads are carried by machined surfaces on the perimeter of the lugs, slightly larger in width than thickness of the walls of the tubular members. 
     U.S. Pat. No. 5,082,128 discloses a quick-connect system where the connectors on the top chords have hook-like male lugs and female lugs with spaced members capturing a horizontal pin between them. FIGS. 10 a - 10   c  show how the hook-shaped member can be fit in place while the boom sections are not parallel, with a rotary motion (about the axis of the pins) bringing the boom sections into parallel alignment and mating up bearing surfaces on the end of each male lug with the inner face of each female lug. The horizontal neutral axis of the top chords (which appear to be tubular in cross-section) intersect the centerline of the pin, but does not intersect the compressive load bearing surface, nor is the compressive load bearing surface symmetrical about the horizontal neutral axis. 
     It would be preferable if compressive load bearing surfaces on connectors were symmetrical about the horizontal and vertical neutral axes of the chords to which they were attached. This would allow compressive loads to be transmitted through the connectors without creating bending moments in the chords. Also, chords having a right angle cross-section are frequently used on boom sections, and quick-connect systems for such chords would be useful. 
     U.S. Pat. No. 5,199,586 discloses quick-connect sectional boom members that have compressive load bearing surfaces that are not only symmetrical about the vertical and horizontal neutral axes of the chords to which they are attached, but are intersected by a line that is formed by the intersection of these neutral axes. 
     While the design of the connector of FIGS. 16-18 of the &#39;586 patent have met with commercial success, and allow quick boom assembly when the boom is being constructed in a horizontal fashion, there are times when boom construction would be better carried out in a vertical fashion. For example, when there are job site space constraints, it is not always possible to construct a long main boom and a luffing jib boom on the ground in a layout position. Under these conditions, it is desirable to construct the main boom and just the luffing jib boom butt and luffing jib struts. These components are then boomed up until the luffing jib boom butt hangs vertical. It would be desirable if the next section of luffing jib boom could be brought in and connected while the connection points are as close to the ground as possible. To achieve this, the next section of boom should be oriented horizontally, and the top chord connection made. To do this, it is necessary to have a connection system that will then allow the boom section to rotate 90° about the top chord section while the luffing jib is further raised and the new section of boom is allowed to swing under the luffing jib boom butt into vertical alignment. Thus, an easy, quick-connect system for boom sections that allows for top chord connections that can rotate through 90° would be a great improvement. 
     SUMMARY OF THE INVENTION 
     A rotatable connection system for boom sections has been invented. With the invention, boom sections can be added to a boom being constructed in either a horizontal layout configuration or in a vertical configuration, such as adding a boom section onto a hanging luffing jib boom butt. 
     In a first aspect, the invention is a crane having a boom with a rotatable boom section connection system, the crane having an upper works rotatably mounted on a lower works, the upper works including a load hoist winch, the boom comprising at least a first and second boom section each with a longitudinal axis and a first and second end, the second end of the first section being coupled to the first end of the second section; at least one male connector on the second end of the first section coupled to a female connector on the first end of the second section; the male connector comprising a base and a protrusion, the base and protrusion each having an extension in a direction generally perpendicular to the longitudinal axis of said first boom section, the extensions and protrusion defining a socket; the female connector comprising two protrusions spaced apart at a distance such that the protrusion of the male connector fits between the two protrusions, the female connector further comprising a coupler connected to at least one of the protrusions and extending toward the other protrusion and fitting within the socket of the male connector; and a retainer connected between the extensions of the male connector preventing the male and female connectors from uncoupling. 
     In a second aspect, the invention is a sectional boom member with a rotatable connection system comprising a boom section having a longitudinal axis, a first end and a second end, and each end having at least three connectors, the at least three connectors of said first end designed to mate with three connectors of a second end of an identical boom section; a first of said at least three connectors on said second end comprising a male connector having a base and a protrusion, and shoulders on the base on at least two sides of said protrusion, the protrusion and base each having an extension in a direction generally perpendicular to the longitudinal axis, the extensions cooperating with the protrusion to define a socket, each of said extensions having an aperture therethrough, the apertures being in line with one another along a line generally parallel to the longitudinal axis; a first of said at least three connectors on said first end comprising a female connector having two protrusions spaced apart at a distance greater than the width of the protrusion on the male connector and a coupling pin spanning between the female protrusions, the coupling pin having a size and being shaped to fit within the socket of the male connector; a retaining pin fitting through the aligned apertures of the male connector for retaining a coupling pin of a female connector of an identical boom section within the socket, thereby preventing the male and female connectors from becoming uncoupled; and the ends of the protrusion on the female connectors having abutment surfaces that are shaped to contact the shoulders of a mating male connector of an identical boom section to transfer compressive loads between the boom sections. 
     With the invention, a horizontally orientated boom section can be added to a hanging boom. The coupler of the female connection is placed in the socket of the male connector and the retainer is put in place to keep the male and female connectors coupled. The assembly is then boomed up, the weight of the new section being carried by the coupler. The new section is free to rotate until it also is hanging nearly vertically. The section is then swung into an aligned position and lower connector pins can be inserted to secure the bottom connectors. This method of adding sections and booming up is continued until the desired luffing jib boom length is assembled. 
     These and other advantages of the invention, as well as the invention itself, will best be understood in view of the drawings, a brief description of which is as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a typical crane with a sectional main boom and luffing jib boom to which the present invention may be applied. 
     FIG. 2 is a side elevational view of a preferred embodiment of a rotatable connection system of the present invention showing two boom sections during perpendicular engagement of the sections. 
     FIG. 3 is an enlarged, partially sectional, side elevational view of one of the top chord connections depicted in FIG.  2 . 
     FIG. 3 a  is an end view of the male connector shown in FIG. 3 without the retaining pin. 
     FIG. 3 b  is an end view of the female connector shown in FIG. 3 without the coupling pin. 
     FIG. 4 is a side elevational view of the boom sections of FIG. 2 in an aligned vertical relationship. 
     FIG. 5 is a side elevational view, similar to FIG. 2, but with two boom sections in a near horizontal engagement. 
     FIG. 6 is an enlarged, partly sectional side elevational view, similar to FIG. 3, showing a top chord connection of the boom sections of FIG.  5 . 
     FIG. 7 is a side elevational view of the boom sections of FIG. 5 in an aligned horizontal relationship. 
     FIG. 8 is an enlarged, partly sectional view, similar to FIG. 6, showing the top chord connection when the boom sections are in an aligned, operational position. 
     FIG. 9 is a top plan view, partially in section, of the connectors taken along line  9 — 9  of FIG.  8 . 
     FIG. 10 is a bottom plan view of the preferred boom sections of FIG. 2 showing the bottom connectors being brought into position. 
     FIG. 11 is an end view taken along line  11 — 11  of FIG.  10 . 
     FIG. 12 is an enlarged plan view of the boom sections of FIG. 10 with the connectors in an engaged relationship, also showing a hydraulic cylinder used to force a bottom connection pin into place. 
     FIG. 13 is an enlarged plan view similar to FIG. 12 with the hydraulic cylinder extended and the bottom connection pin in place. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS OF THE INVENTION 
     For ease of reference, designation of ″top, “bottom,” “horizontal” and “vertical” are used herein and in the claims to refer to portions of a sectional boom in a position in which it would typically be assembled on or near the surface of the ground. These designations still apply although the boom may raised to different angles, including a vertical position. 
     The typical crane  10 , as shown in FIG. 1, is comprised of upper works  12  rotatably mounted on lower works  11  which, as shown, may include self propelled crawler tracks. The upper works  12  typically has a counterweight  13  attached thereto. In the crane embodiment depicted, the counterweight  13  is supported on a separate counterweight trailer  18 . The upper works  12  also supports a back hitch  14  and mast or gantry  15 , as well as a pivotally mounted boom  20 . A winch with a load hoist line wound thereon (not shown) is also mounted on the upper works. Live rigging and a pendant  16  connects the top of the boom  20  to the gantry  15  and is used to adjust the boom angle. A pendant  19  connects the top of the gantry is to the counterweight  13 . 
     The crane  10  as depicted also includes a luffing jib  90  with superstructures  91  and  92  and control lines  93  as is typically used to control the angle of the luffing jib  90  secured in pivotal relationship to the top end of boom  20 . 
     In conventional cranes, the boom  20  is made of several sectional members, including a boom butt  21 , boom insert sections  22 ,  23 ,  24 ,  25 ,  26 ,  27  and  28 , which may vary in number and be of different lengths, and a boom top  29 . The sectional boom members  21 - 28  typically are comprised of multiple chords. The luffing jib boom  90  is likewise made of a luffing jib boom butt  94  and boom insert sections  95 ,  96 ,  97 ,  98 ,  99  and  100 , which like boom insert sections  22 - 28  may vary in number and be of different lengths. A luffing jib top end (not shown) is added to the end of the last insert. 
     In the embodiment shown in FIG. 2, each luffing jib boom section  99  and  100  has a rectangular cross section with a chord at each corner. The sections  99  and  100  each have a longitudinal axis  41 , as well as first and second ends. There are two top chords  31  and two bottom chords  33  (only one of each of which can be seen in the side view) interconnected by intermediate lacing or lattice elements  35 . In the embodiment shown, the chord members are made of steel with circular cross section. Each chord member has a vertical neutral axis and a horizontal neutral axis. In the case of chords with circular cross sections, the horizontal and vertical neutral axes intersect at a line  40  which is at the centerline of the chord (FIG.  3 ). Compressive loads applied at the intersection  40  of the vertical and horizontal neutral axes of a chord, or symmetrically about the horizontal and vertical neutral axes, will not induce bending moments within the chord. 
     The preferred rotatable connectors are described as being provided on the top chords  31  of a boom section. Connectors for bottom chords  33  are also disclosed. Mating connectors are attached to abutting ends of the chords of the sectional boom members. The mating connectors generally have a male and female relationship. Thus, there are two top chord female connectors  36  and two bottom chord female connectors  38  on each boom section, generally but not necessarily on the same end of the boom section, as well as two top chord male connectors  37  and two bottom chord male connectors  39  on opposite ends of the boom section from the respective top and bottom chord female connectors. Thus, when two boom sections, such as sections  99  and  100 , are brought together for assembly, the two top chord female connectors  36  of section  100  mate with the top chord male connectors  37  of section  99 , and the bottom chord female connectors  38  of section  100  mate with the bottom chord male connectors  39  of section  99 . Since the connectors on all of the sections  23 - 28  of main boom  20  and sections  95 - 100  of luffing jib boom  90  are identical, the foregoing reference numbers  31 ,  33 ,  35 ,  36 ,  37 ,  38 ,  39  and  40  are used in all of the figures, whether showing main boom sections or luffing jib boom sections. 
     FIGS. 2-4 are used to depict the procedure in which a second boom section is added to a first boom section that is part of a vertically hanging boom, and therefore luffing jib boom sections  99  and  100  are depicted. FIGS. 5-9 are used to depict the procedure in which a second boom section is added to a horizontally extending first boom section. While this procedure can be used for connecting luffing jib boom sections, it is depicted using main boom sections  23  and  24 . Of course, there may be times when it would be desirable to connect main boom sections using a rotational procedure depicted in FIGS. 2-4. 
     As best shown in FIGS. 3 and 3 a , the male connector  37  has a base  52  and a protrusion  54 . The protrusion  54  extends perpendicularly from the base  52 , in a direction generally parallel to the longitudinal axis  41  of the crane boom section  99 . Extensions  56  and  58  extend respectively from the base  52  and the end of protrusion  54  in a direction generally perpendicular to, and directed outwardly of, the longitudinal axis  41 . Each extension  56  and  58  has an aperture  57 ,  59 , respectively. The apertures  57  and  59  are in line with one another on a line that is generally parallel to the longitudinal axis  41 . The extensions  56  and  58  cooperate with the protrusion  54  to define a socket  51 . As shown in FIG. 3 a , there are two shoulders with machined abutment surfaces  53  and  55  located on the base  52 , one on each side of protrusion  54 . 
     As best seen in FIG. 3 b , the female connector  36  also has a base  72  and has two protrusions  74  and  76  extending generally perpendicularly from the base  72 . The protrusions  74  and  76  are spaced apart at a distance greater than the width of the protrusion  54  on male connector  37  such that the male protrusion  54  fits between the female protrusions  74  and  76 . The female connector also comprises a coupler sized and shaped to fit within socket  51 . The coupler will connect to at least one of the protrusions  74  and  76  and extend toward the other protrusion. In the preferred embodiment depicted, each of the protrusions  74  and  76  have a round hole  75  and  76 , respectively, through the protrusion, and the coupler comprises a cylindrically shaped coupling pin  78  extending through the holes  75  and  77 . The coupling pin  78  thus spans between the female protrusions and is preferably free to rotate within the holes. Preferably, the coupling pin  78  extends through the holes and cotter pins (not shown) or the like are used to capture the pin  78  to prevent longitudinal movement or dislodgement of the pin. The protrusions  74  and  76  have abutment surfaces machined onto their ends  71  and  73 , respectively. 
     The length of protrusion  54  on the male connector is less than the length of the protrusions  74  and  76  on the female coupler. As a result, the abutment surfaces  71  and  73  on the ends of female protrusions rest against the machined abutment surfaces  55  and  53 , respectively, when the male and female connectors are placed in a mating position. Thus, when the male and female connectors are fully engaged, compressive loads on the boom are transferred across the abutment surfaces  71 ,  73  and  55 ,  53 . 
     When the connectors  36  and  37  are coupled, the coupling pin  78  fits within socket  51 . Preferably, the inside corner of socket  51  is machined to the radius of the cylindrical coupling pin  78 . As seen in FIG. 3, once the connectors are coupled, a retainer is connected so as to extend between and be secured to the extensions  56  and  58  of the male connector  37  to enclose the coupling pin  78  within the socket  51  and prevent the connectors from uncoupling. Preferably, the retainer is a retaining pin  62  which extends through apertures  57  and  59  in the extensions  56  and  58 . 
     As shown in FIGS. 2 and 4, the connectors of the present invention allow sectional boom members to be connected and then rotate through a full 90° angle. In FIG. 2, a first boom section  99  is suspended vertically. A second boom section  100 , suspended horizontally, such as by an assist crane (not shown), is brought into place where the female connectors  36  of section  100  can be coupled to male connectors  37  of section  99 . Even though the longitudinal axes  41  of the two boom sections are perpendicular to one another, the coupling pins  78  on the female connector  36  can still be placed in the sockets  51  of the male connectors  38 . After retaining pins  62  are in place, the assist crane can let the free end of section  100  swing downwardly and underneath the first section  99 . The boom sections rotate about the coupling pins  78  until the longitudinal axes  41  of each boom section are brought into an aligned relationship (FIG.  4 ). At this point, the abutment surfaces  53 ,  55 ,  71  and  73  on the male and female connectors are engaged, and the connectors on the bottom chords  33  are pinned together, as described more fully hereafter. 
     FIGS. 5-9 show the procedure for connecting boom sections of the preferred embodiment of the invention together when the connection is made to a boom section in a horizontal position. As shown in FIG. 5, a first boom section  23  is horizontal, perhaps supported by blocking on the ground. The second boom section  24  is brought in at a nearly horizontal angle, such that the longitudinal axes of the two boom sections  23  and  24  are nearly parallel. Once again, the coupling pin  78  fits within socket  51  when the first and second boom sections are initially coupled together (FIG.  6 ). The shape of the socket and coupling pin  78  cooperate to cause the longitudinal axes of the two boom sections to align with one another as the male and female connectors  37  and  36  are completely engaged (FIGS. 7,  8  and  9 ). 
     FIG. 10 shows the engagement of the connectors on the bottom chords  33 , which as noted above are pinned together after the male and female connectors  37  and  36  on the top chords  31  are fully engaged. The bottom chords each have connectors which are more conventional in nature. On one end of each bottom chord, the connector  39  has one protrusion and on the other end, the connector  38  has two protrusions. When two boom sections are brought into connecting alignment, the single protrusion on the connector  39  on a second end of the first boom section will fit in between the two protrusions on the connector  38  on the first end of the second boom section. Each of the protrusions on connectors  38  and  39  have aperture through them. Two bottom connection pins  64  and  65  are inserted through the apertures to secure the second ends of the bottom chord members  33  on the first boom section to the first ends of the bottom chord members  33  on the second boom section. 
     In the preferred embodiment of the invention, the boom section includes brackets  81 ,  82 ,  83  and  84  used to mount a hydraulic cylinder  85  (FIGS. 11-13) which in turn is used to insert and remove bottom connection pins  64  and  65 . Preferably, brackets  81  and  84  hold one end of pins  64  and  65 , respectively, in place for insertion with the other end of pins  64  and  65  being held in the aperture through the protrusion on connector  38  closest to the center of the boom section. A hand-held hydraulic cylinder  85  is fitted to either bracket  82  or  83 , depending on which pin is to be inserted. As shown in FIG. 12, the piston end of cylinder  85  is held in bracket  82  and the rod end of cylinder  85  connects to the head of pin  64 . Extension of the cylinder  85  drives the pin  64  through the apertures in the protrusions on the aligned connectors  38  and  39  (FIG.  13 ). The cylinder  85  can also be used to retract the pins  64  and  65 . 
     As noted previously, it is preferable to have the abutment surfaces on connectors symmetrical about the horizontal and vertical neutral axes of the chord to which the connectors are attached. As shown in FIG. 3 a  the abutment surfaces  53  and  54  are symmetrical about the horizontal neutral axis  45  and the vertical neutral axis  46  of chord  31  to which male connector  37  is attached. Likewise, as shown in FIG. 3 b , the abutment surfaces  71  and  73  are symmetrical about the horizontal and vertical neutral axes  45  and  46  of the chord  31  to which female connector  36  is attached. In this manner, not only can the boom sections of the present invention be brought into contact while perpendicular to one another and rotated into an aligned position, but in use, the compressive forces are transferred through the connectors without causing a bending moment in the chord  31 . 
     The connectors of the present invention also allow boom sections to be connected from a nearly parallel arrangement, adding to the versatility of the crane boom sections. The sections can thus be used to construct a main boom that is laid out in a horizontal fashion, or a luffing jib boom that is assembled in a hanging vertical position. 
     Besides the preferred embodiment of the invention depicted in the Figures, there are other embodiments contemplated. For example, instead of having a pin spanning between the female connector protrusions, lugs could be affixed to one or both of the inside faces of the protrusions. These lugs would fit in the socket  51  and be captured by the retaining pin  62 . Other types of retainers, such as straps, could be secured between the extensions  56  and  58 . 
     The socket and coupler could be exchanged between the male and female connectors. The male connector could have a coupler pin extending outwardly from both sides of a single protrusion and the female protrusions could each be shaped with a socket and retainer. 
     It should be appreciated that the apparatus of the present invention is capable of being incorporated in the form of a variety of embodiments, only a few of which have been illustrated and described above. The invention may be embodied in other forms without department from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the invention is therefore indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.